Golang print struct field names. This should give you some form of output: if data.

Golang print struct field names FieldByName(field. Slice(planets[:], func(i, j int) bool { return planets[i]. Printf("%+v\n", struct) Print both name and value. Name var Foo_Baz = reflect. Println(p) // Prints: In this Golang article, we will write programs to print struct variables. Apr 13, 2023 · In this case, the second field "Field2" is an int type. Println(field. It defines a myStructure struct with a single string field, bar. Improve this answer. Name() // *int ptr. That results in printing ' Paul 0 ' I like that struct field Name is changed , but what is the correct way to keep Age field ? Sep 2, 2020 · Names of those fields should be the values of Request. type Student struct { id int name string "Why would using just Foo cause recursion?" - @Chris The json package checks if a type has UnmarshalJSON() defined, and if so it calls that implementation. However, I would very very strongly recommend a thorough code review, because there should be no situation where you actually I am trying to check struct fields using Go reflect package. Jul 8, 2017 · You need to use sqlx. You need to ensure that the fields in your struct are exported, or basically start with a capital letter. Name and their values should be the values of Request. Using %+v simplifies the process and is especially useful for Now when you want to print a struct, you can do: fmt. For more precision, you can use %#v to print the object using Go-syntax, as for a literal: %v the value in a default format. Fields[0]. You switched accounts on another tab or window. Feb 17, 2014 · Go uses case to determine whether a particular identifier is public or private within the context of your package. So: type Test struct { Field string `bson:"Field" json:"field"` OtherField int `bson:"OtherField" json:"otherField"` } Could generate something like: In this example, we define a Person struct and use Printf to print the individual fields with appropriate formatting. Code package main import ( "fmt" ) type MyEnum int const ( Foo MyEnum = 1 Bar MyEnum = 2 ) func (e MyEnum) String() string { switch e { case Foo: return "Foo" case Bar: return "Bar" default: return In your printJSON function you were just printing out the slide of fruits the basket. An if statement to pick up the fields you want to Marshal, and. I am trying to do something like below stuff, where I want field name age to get assigned from variable test. Some of those arguments are as below: %v the value in a default format %+v the plus flag adds field names %#v a Go-syntax representation of the value Example 1 Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company (Update: to put the output into a string instead of printing it, use str := fmt. Any help is appreciated. The You could use the stringize operator and define a print function for the variable name together with the variable declaration: #include <stdio. In this example, we define a Person struct with Name, Age, and Address fields. NumField()) for i := range names { names[i] = t. – Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Q: How do I pretty print a struct in Golang? A: To pretty print a struct in Golang, you can use the following code: fmt. OUTPUT: Name: John Doe Age: 30. The closest thing I can think of, but it's damn ugly so do not take it as the answer is something like this:. %#v value in go-syntax %+v when value is Struct, also print field names %T type of the value in go-syntax %% literal Dec 9, 2015 · I am new to golang, and got stuck at this. package main import "fmt" type Foo struct { name string } // SetName receives a pointer to Foo so it can modify it how to modify struct fields in golang. e. You may be able to load a set of types via reflection and generate a set of constants for the field names. DeepEqual() can do it because it has access to unexported features of the reflect package, in this case namely for the valueInterface() function, which takes a safe argument, which denies access to unexported field values via the Value. To review, open the file in an editor that reveals hidden Unicode characters. something like: item := Item How to print struct with String() of fields? 7. Name) fmt. Slice:. The most simmilar construct to {} would be a map but I'm pretty sure your question comes from the differences in dynamic and static languages. type SomeFormInput struct { Name string Password string `json:"-"` } And as a final option, you could filter the log output, prior to sending it to the logger. All private fields, methods and functions starts with lowercase char. Method 4: Implement a custom ToString() function for a struct First off, the most straightforward way to print a struct in Go is using the fmt package. May 3, 2020 · Go language provides inbuilt support implementation of run-time reflection and allowing a program to manipulate objects with arbitrary types with the help of reflect package. See How to define multiple name tags in a struct on how you can define multiple tags on one struct field. Printf() with format “verbs” %+v or %#v. switch t. Here, there is no concept of classes, instead of that structs are used to represent a collection of related fields or properties. TemplateId is nil. Name, value. UpdatedBy. Marshal because it is not part of the package containing your code. NullString field sql. FieldByName Function. To print the data of the struct variables, we use the fmt. That said, a couple of ways to skin the proverbial cat: Both methods assume a Only field names that begin with an uppercase letter are exported – and therefore available to the reflection model. Axis < planets[j]. Like so: fmt. I did some Googling and I can not find any requirements for struct field names regarding this. Println(getProperty(&v, "X")) } func getProperty(v *Vertex, property string) float64 { m, _ := json. My goal is to pass an object of any struct type and then to parse all field to get name and values of different fields, recursively. This flag adds field names. DeepEqual(). Golang print struct variables on console using 4 different methods. You shouldn’t name your variables after their types for the same reason you wouldn’t name your pets “dog” or “cat”. Note that the JSON text contains the field names with lowercased Apr 13, 2017 · I’m trying to get help on what’s the recommended way of doing the following. If you worry about losing the convenience of shorter field names, or different marshalled results, then use embedding instead of a named field: type Big struct { Small // Embedding C float D byte } Feb 27, 2016 · Use encoding/json package to Unmarshal data into struct, like following. You can still do it, but The example below shows how you'd print a particular field value of a struct: type child struct { name string age int } type parent struct { name string age int children child } func main() { family := parent{ name: "John", age: 40, children: child{ name: "Johnny", age: 10, }, } fmt. If no node ever can be a "Leaf" and a "Root" at the same time you can spare one field and have a single additionalData float32 // leafPenetration for Leafs and padDim for Root nodes. Understanding how to print struct contents in Golang is crucial for effective development and debugging. 19. ValueOf(&x) value := ptr. When you changed the fields to be upper case, they became public so could be exported. The Printf()function. struct field ApiVersion should be APIVersion. By leveraging built-in formatting methods, implementing custom printing techniques, and exploring different output strategies, developers can gain deeper insights into their data structures. Exporting structs in go. Declare struct field name as "type" 0. NumField(); i++ { fmt. Println(“%+v”, myStruct) This will print the struct in a format that includes the struct’s name, field names, and values. FieldByName to get the Value of a struct field if you want to map to struct fields. from the fmt doc: %v the value in a default format when printing structs, the plus flag (%+v) adds field names Apr 16, 2020 · Parse struct field pointers with reflection in Golang Hi guys, I'm in trouble, can't make my code running properly. Aug 3, 2018 · I must parse the xml output of an legacy system where they for some reason thought that it will be smart to add the IDs of values as tag names. We can use the formatted I/O feature of the Printf() function to print the structure's fields along with their names using the %+v argument. Or you can use both types in your structure, and make method Details() which will return right pattern. Technically your first example will work, but you are trying to access the Value field with dot notation, even though you declared it to be a map:. package main import ( "fmt" "reflect = rt. Jul 31, 2020 · But none of this is working (How do i display registrant name in one field, then display technical name in another? i'm obviously messing up the templates big time and my understanding of it is a bit skewed). Field(1). e fmt. If you're using JSON, you could parse the data using the tokenizing json. Obviously, this would not present a challenge if it were for one struct but I need the function to be dynamic. for field := range emailDef. The for range statement is applicable only to:. 2. display(&valueValue) So it is being called with an argument of type *interface{}. Eventually, I'd like to make the result into a map[string]interface{}, but this one issue is kind of blocking me. Select when you are selecting multiple rows and you want to scan the result into a slice, as is the case for your query, otherwise use sqlx. Fields with a nil value should not be returned. You can also use a type Info map[string]interface{} instead of your struct. Ask Question Asked 7 years, 2 months ago. Modify() . f is a legal selector that denotes that field or method f. testCases := [] type structName struct { id sql. When printing you will get the following result in your console: result: {Id:1 Title:My Title Name:My Name} Print a nested struct in your console in go (golang) Use the fmt. When you print the struct, it's going to print the values of the types contained - in this case the pointer value of a string pointer. So it does seem to me that %#v and %#+v should be expected to generate identical output. Time } func main() { d1 := Doc{ Person: Person{"Bob", 21 Jun 10, 2022 · How to represent Golang struct with variable field names [duplicate] Ask Question Asked 2 years, 3 months ago. But in the second way i have mentioned in below, complex or custom types can not be checked (example uuid. As you get into it, those functions will start to make more sense, as you encounter the problems and start to understand the solutions. The reflect. Inside the for loop, you have a recursive call to display:. Rows. Golang Pretty Print Struct Learn how to pretty print struct in Golang with a simple example. , %s for strings, %d for integers). Preparation: Blend them in a good proportion. p := Person{Name: "John", Age: 30} fmt. By explicitly to disambiguate the two fields). For example, to name the fields CardID, Name, CardSet, and Type in the JSON output, you can define your struct like this: type Card struct { CardID string `json:"cardId"` Name string `json:"name"` CardSet string `json:"cardSet"` Type string `json:"type"` } The json:"<name You need to make the field exported,ie you may declare the struct as. Either just print the thing how you want, or implement the Stringer interface for the struct by adding a func String() string, which gets called when you use the format %v. Kind() { case reflect. Now I want to extract only field names that have associated values. For example, the data may Feb 2, 2014 · how could I get the field name, value and join it into a string. package main import "fmt" type Person struct { Name string Age int } func main () { p := Person { Name : "John Doe" , Age : 30 } fmt . The json package only accesses the exported fields of struct types (those that begin with an uppercase letter). Put another way: encoding/json does not support multiple struct fields for the same JSON key. Printf("%v\n", struct) Print struct value only. Here is the example. To use different field names in the JSON output, you can use struct tags. ValueOf(v)). Println(Foo_Bar, Foo_Baz) } Summary. Unmarshal will do its best to place the data where it best aligns with your type. Set(reflect. From there, you can list fields of the dynamic value stored in the interface. A third variation is %+v which will include the field names, but not the struct type. Example: type Point struct { X int Y int } var reply interface{} = Point{1, 2} t := reflect. Ptr package main import "fmt" // This `person` struct type has `name` and `age` fields. The data I get from HTTP call is in struct slice type and the response may have 10 fields for the struct but I only need to print out several related fields as tabular ascii format for users to see. If the type is declared in the same package, you can set reflect. Methods of Finding the Size of the Struct in Golang: In Golang, the unsafe package provides functions to find the size of variables. Feb 24, 2018 · From a 3rd party: package lib type Bar interface{ Age() int } Foo(b Bar) int This doesn't compile because Age is both a method name and field name: package main import "lib" type Person st Oct 27, 2017 · Where the code comment "print the contents of listOfPeople is where I would like to be able to print a 'person'. 7. It makes it Aug 26, 2017 · Within a struct, non-blank field names must be unique. Print list of fields in struct with delimiter. Unmarshal(contents, &result) fmt. func Sprint(v interface{}) string { t := reflect. You know best as the author but remember this; keep the type names out of the variable name. valueValue := reflectValue. It is common in Go to compose larger structs through nesting: type Organization struct { Name string Owner User } type Repository struct { Name string Org Organization } repo := &Repository{ Name: "go", Org: Organization{ Name: "golang", Owner: User{Name: "rob"}, }, } I have a struct: type Human struct { Head string `json:"a1"` Body string `json:"a2"` Leg string `json:"a3"` } How can I get the struct's field name by providing JSON tag name? json. You need it to create the user record, at which point you'll store a hash in your data store. The encoding/json package to Marshal the fields of your liking. Name Dec 6, 2018 · Golang get struct's field name by JSON tag. in particular, have not figured out how to set the field value. g. Golang: print struct as it would appear in source code. “A variable’s name should be independent of its type. Value. Sprintf() and the String() method. Elem() for j := 0; j < v. You signed out in another tab or window. But, it would convert all the number values to float64 so you would have to convert it to int manually. To parse the password in a json document you can simply unmarshal twice. Struct: fmt. ". In addition, you can't scan directly into a Group struct because none of its fields are tagged (unlike the Course struct), and the Course field isn't embedded. Each verbs converts a value to a particular string format. – Marco Leogrande. Basically I just want to create a slice with different variables ( strings ) and then loop through the slice and replace the markup {{}} with the actual values. Passing a slice of pointers []interface{} to Rows. This guide will help you rank 1 on Google for the keyword golang pretty print struct. How to Dec 15, 2021 · Old answer (not relevant anymore, only informative) At some point in early 2022 while this feature was still in development, your example did work if you added ~:. fmt. Marshal. TypeOf(Foo{}). In the main() function, an instance of myStructure is Go uses case to determine whether a particular identifier is public or private within the context of your package. Name func main(){ fmt. Sep 19, 2019 · Then if you have a Big struct, you also have a Small: Big. Here is my 'Event' model: type Event struct { Event string `json:"Event"` Values Values `json:"Values"` } type Values struct{ Id string `json:"Id"` } Sep 9, 2024 · I have a struct that will get its value from user input. Addr to get a pointer to the destination value. There are two ways to do this. Println(emailDef prints the type of a value in golang; print struct with keys golang; golang iterate via structure fields; golang print all headers; how to print string in golang; strings fields golang; golang all data structures; what is struct in golang; go type struct; Structs in Golang Golang get struct's field name by JSON tag. I want to print out selective fields in a struct slice as nice tabular interface. "no returns or refunds" signs Why did the "Western World" shift right in post Covid elections? 80-90s sci-fi movie in which scientists did something to make the world pitch-black because the ozone Apr 12, 2021 · You can try initializing a new struct with fields from old struct but that would also depends on field types you have and if you want those fields to hold same pointers as in first struct. Also, this concept is generally compared with the classes in object-oriented programming. when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value Jan 29, 2018 · I have a golang struct, and have created a String() method for use in the program's normal operation. Dynamically built formatting strings in Golang. 〔see Golang: Basic Types〕 Some verbs take in a value of specific type. Y } func (b *B) Sum() int { return b. Println(person{name: "Alice",test: 30}) } This is just sample code replicating my use case. UUID). Here, there is no concept of classes, instead of that structs are used to represent a collection of related fields Go’s fmt package provides a convenient %+v format verb specifically designed for printing structs. So far I have: type MultiQuestions struct { QuestionId int64 QuestionType string QuestionText s From Go's manual: when printing structs, the plus flag (%+v) adds field names. Printf(“%v”, structName). dynamic access like that is not possible without reflection (which you shouldn't use here). Modified 2 years, 3 months ago. A struct has different fields of the same Use a struct value and the name of the field to get the tag: // jsonTag returns the json field tag with given field name // in struct value v. Given that I don't think the docs can be read another way, and given that %#+v is bound to be unusual, I'm Nov 16, 2017 · How do I find which struct field is different when comparing two structs using reflect. Axis }) The sorting changes the array, so if you really want you can continue to use the array instead of Nov 18, 2024 · Just to be clear, all these packages are my own, so if I change the name of a field, I would know about it. By Xah Lee. X + a. Date: 2022-03-06. type Sample struct { Name string Age int } All we have to do is to add %+v to our print function. Follow edited Jan 30, 2014 at 14:42. Jan 6, 2014 · For each []byte, this example prints the name of the field and its data (in hex). Indirect(rv). The code I have at the moment: Aug 5, 2018 · Also have a look at the DeepEqual implementation, or start reading through the JSON encoder/decoder. Example I don't really think there is. The type descriptor is the same as rtype - the compiler, the runtime and the reflect package all hold copies of that struct definition, so they know its layout. For example, the following code declares a struct called `User` with two fields: `name` and `email`: type User struct {Name string Email string} Structs can be How to list the fields and methods of a struct, in GoLang dynamically? For eg, I want to get the output as id, name, age, and all the method names. Field(i). ValueOf(u) for i := 0; i < Jul 16, 2019 · Golang docs provide a clear guidance on how to name single-method interface (by appending "-er"). Type type descriptor. Elem() ptr. You can marshal the struct and unmarshal it back to map[string]interface{}. Code example on printing a struct in go (golang) You can't do that. X + b. To print struct variables in Go, you can use the following methods: Use fmt. String Apr 23, 2018 · Update your struct to this , to unmarshal api response you need to export your structure's fields i. The Int() method is used to convert the value of the field to an int and it's printed on the console. S. type Type interface { ~struct{ A string } } but it only worked for structs exactly defined as struct{ A string } and nothing else. Jackson with JSON: Unrecognized field, not Jun 13, 2024 · type User struct { Name string Age int } func (u *User) Modify() { *u = User{Name: "Paul"} } in the main() I am defining struct literal &User{Name: "Leto", Age: 11} then call u. Field(i) rv := reflect. Jan 21, 2014 · I'm looking to iterate over the string fields of a struct so I can do some clean-up/validation (with strings. Test) You can also parse Test to Sep 9, 2024 · I am trying to loop through the individual fields of a struct applying a function to each field and then return the original struct as a whole with the modified field values. You could also reference each value in the format which is a struct. The solution, most likely, would be to not embed the types, but actually create a struct with explicit Mar 6, 2022 · Some verbs take in a value of any type. Finally, this: A field or method f of an embedded field in a struct x is called promoted if x. See here for details on the rules of what gets exported and what does not: [Where. Providing accessor methods with proper names and which check Category might be a good idea. Printf function along with appropriate formatting verbs for each field type (e. type Animation struct { Name string `json:"name"` Repeat int `json:"repeat"` Speed The code showcases how to customize a Go struct’s string representation using fmt. why the language doesn't compile the source code "assign to a field-of-a-struct-in-an-array" to "create a temporary variable of the struct-in-an Mar 12, 2015 · There is normally no reason to use an array instead of a slice, but in your example you are using an array, so you have to overlay it with a slice (add [:]) to make it work with sort. TypeOf(your_struct). Columns to get column names and positions. This will print the struct in the format of a map. I've read everything i could, i tried to divide the structs and serve as separate structs, etc. type t struct { fi int; fs string } var r t = t{ 123, "jblow" } var i64 int64 = 456 getting Name of field i - this seems to work. Basically, you have to do it yourself. Fields { fmt. Value. Sprintf(). Printing Nested Struct Composition. To access this function, one needs to imports the reflect package in the program. package yelk type PhoneOptions struct { Oct 1, 2019 · A validator package gives me back strings like this if a given field in my struct doesn't pass the validation: myString := "Stream. Kind() // reflect. That said, a couple of ways to skin the proverbial cat: Both methods assume a Apr 26, 2023 · An additional elaboration that I find is often useful is to add this to your person: . go file . all entries of an array, slice, string or map, or values received on a channel. Interface() method if safe=true. NumField(); j++ { Go doesn't have builtin struct iteration. type MyStruct struct { Field MyEnum } Here is a sample program with exported and unexported fields. We then create a variable emp of type Employee and print it. Fields is a string array ["TemplateId"] I want to check if those fields are in the EmailTemplate struct and if they are nil. Structs in GoLang. I had two potential uses in mind: White box testing, which your solution definitely works for, but also a parser, which converts strings to the objects in the other package, whose efficiency would benefit from bypassing the usual constructors for the structs but your Jul 22, 2024 · In this example, Employee is a struct that has three fields: Name, Age, and Salary. I don't see how else the read the current docs. Viewed 1k times 1 This How to print struct variables in console? 1024. When doing the comparison, just compare the embedded fields: type Person struct { Name string Age int } type Doc struct { Person Created time. So, output would be of type: UserList []string Apr 16, 2015 · So I found some code that help me get started with reflection in Go (golang), but I'm having trouble getting a the underlying value so that I can basically create a map[string]string from a struct and it's fields. But what is the best practice to name a multi-method interface that has only a single struct implementing it? In C# the interface would have "I" Dec 28, 2015 · Inside your display function, you declare valueValue as:. It's just to avoid name collisions; call it whatever you want. By are ambiguous and not allowed (you'd have to be able to specify Event. The String() method, overriding the default behavior, formats a string combining a preset message and the bar field’s value using fmt. Therefore only the exported fields of a struct will be present in the JSON output. You don't need it to view, or delete, or update (normally). /foo/foo. Is this possible in golang? In p Jul 12, 2017 · having a rough time working with struct fields using reflect package. Field(i)) } This is a good point. The first way is to use the Printf function of package fmt with special tags in the arguments the printing format arguments. h> /* This declares a variable name together with a function print_name */ #define declarePrintable(type, name) int print_##name() { return printf("%s", #name); } struct type name struct someType { int i; }; I can see no other option than using reflection. Marshal(v) var x type someAPI struct { ApiEndpoint string `json:"apiEndpoint"` ApiVersion string `json:"apiVersion"` } And I get these warnings struct field ApiEndpoint should be APIEndpoint. /main. It prints the struct’s field names along with their values. Creating and printing a basket struct and adding a JSON tag to the field Basket achieves what you want: I want to return the name of a struct attribute using the reflect package. go: Sep 20, 2015 · Export the struct fields by starting them with capital (upper-case) letters. Printf("%+v\n", t. sort. CreatedBy. Type(). Printf("%+v", mystruct) Share. The function takes a Dec 25, 2015 · The problem is that you're embedding both CreatedBy and UpdatedBy into Event, so calls to Event. To add package to your module or program just create a lowercase folder and add package name to all files inside. Here's a complete list. access golang struct field with variable. ValueOf(a). emailDef. Value["Imagedata"]) } Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Visit the blog A struct (Structure) is a user-defined type in Golang that contains a collection of named fields/properties which creates own data types by combining one or more types. This should give you some form of output: if data. Commented Jul 22, 2012 at 6:40. So we arrive at the top of the function, then we call Unmarshal() on f, and the json package checks if Foo has UnmarshalJSON() defined, and it does, so it calls it, and so on, to infinite recursion. Printf package and add the flag (%+v). By and Event. Here's how to print Struct. how to loop over a struct and print values? Share Sort by: Best. If size matters you can use %v, but I like %#v because it will also include the field names and the name of the struct type. You could improve on this by taking a custom function to do the printing, so you don't always have to print in hex. // In the case of a struct, we print the names of the fields and recurse. Aug 4, 2012 · Nothing gets printed, because name is empty. Inside the recursive call, reflectType will represent interface{} rather than the type Sep 28, 2021 · Jokes aside, names are hard. ValueOf, you pass it an any (which is an alias for interface{}). Field(0). Ask questions and post articles about the Go programming language and related tools, events etc. NumField()) if visited[t] { // Don't blow up on recursive type definition You can use the reflect. As a general rule, though, any use of the generic interface{} type should be avoided, unless you are writing a large generic framework. Golang program to print struct variables - In this Golang article, we will write programs to print struct variables. To print structs we use the fmt package i. Name" How can i use this string to gain access to the struct field specified in it? I need to reference it Jul 9, 2024 · For anyone else who wants to understand this more, this seems to be a discussion of Addressability - though it seems to mostly focus on pointers, and doesn't explain why this choice was made in the Go Language (i. To avoid making mistakes in common key names you can create constants - that way if you make typo in constant name code won't even compile (and in the end it will be less verbose to write than passing a struct): Jun 13, 2016 · Fields that start with lower case characters are package internal and not exposed, If you want to reference the field from another package it needs to start with an upper case character, eg. Any Type %v default format. If you don't have any instance, then you need to use reflection to display the name of the field of a given struct, as in this example. /foo/MyStruct. type Animal2 struct { Name string Spec string Id uint32 } Try it on the Go Playground. Field() to access the fields. RequestValues. I tried the usual %+v format but it seems to use the String() method instead of showing me all the fields. Scan to get the values. I have an array of structure: Users []struct { UserName string Category string Age string } I want to retrieve all the UserName from this array of structure. NullBool } Share. So if the variable 'name' is onevar it will look in the template for {{onevar}} and replace that with the actual value of the variable . Thanks to Go‘s dot syntax, we can directly access nested struct fields: fmt. TypeOf() function to obtain a reflect. type Role int type User struct { Id int64 Name string Role Role } func ListFields(a interface{}) { v := reflect. ValueOf(&s) value := reflect. Get for a single row. The visibility metadata needs to be stored somewhere and needs syntax to express it. 0. var field = reflect. type Foo []int) If you must iterate over a struct not known at compile time, you can use the reflect package. . Println(family. Open comment sort options. You can try using the package dump, which acts similar to PHP's print_r or var_dump. So how do I set and get a field inside a struct? Working playground. 1. 137. To know whether a field is set or not, you You can only use composite literals to create values of struct types defined in another package if you use keyed values in the literal, because then you are not required to provide initial values for all fields, and so you can leave out unexported fields (which only the declaring package can set / change). Y }. DeepEqual() will (might) call that passing safe=false. type person struct { name string age int } func main() { var test = "age" fmt. Follow answered May 28, 2020 at %#v for a struct is expected to add field names, since those field names will appear in the "Go-syntax representation of the value. reflect. I have tried a couple of things but nothing prints or compilation fails. Trim, Iterate through struct in golang without reflect. FirstName, The Marshal function will return a byte array. Add a comment | 1 . Println(result. Mar 4, 2013 · type A struct { X int Y int } type B struct { X int Y int Z int } Is there any way to achieve the following without needing two methods, given that both access identically-named fields and return the sum of them? func (a *A) Sum() int { return a. Hot Network Questions Implied warranties vs. When I print the struct values then I don't see any difference I had to more or less implement the diff myself, but in this case it works and the diff shows all the field names up to the values which differ. Without attempting to print out a person from listOfPeople the code compiles and runs. Jun 25, 2019 · This is a sample script for dynamically retrieving the keys and values from struct property using golang. You'll have to do this yourself, either by implementing UnmarshalJSON, or by unmarshaling into one field and copying to the other yourself. Basically go expects you to explicitly define the mapping from a struct to your export object, in this case json. Sep 26, 2017 · Now I want to be able to use this struct to register a user and update, delete but also to view. Indirect(reflect. Ok, so lets see how this works. e your structs feilds should be in upper case:. Jul 19, 2014 · I'm trying to build an easy to use templating system. go . imagine you have a struct called EmailTemplate and it has a field called template_id. Eventually it was determined that co opting the capitalization of the first char works best with fewest trade-offs. Println(PrintStruct(a, true)) You may also choose to add a String() method to your struct which just has to call our The simplest way to print out a struct is to use the Println() function from the built-in fmt package. . For example: Name string. Related. Once into your user struct (which doesn't have the password field), and then again into another struct that has only the password field. If you have a Small and you need a Big: Big{S: small}. Print() does not print variable names of Go structs, but it does not mean you cannot do that. %v the value in a default format when printing structs, Acquire the reflect. How can I do that? Here’s my code: package main import "fmt" import "reflect" type Users struct { Name string Password string } func main(){ u := Users{"Robert", ""} val := reflect. Name() to get a name of the ith field of your_struct. Setting values of concrete struct by using Feb 16, 2024 · Declare struct in Go ; Printf Function of fmt Package ; Marshal Function of Package encoding/json; In Go, struct is a collection of different fields of the same or different data types. Println() method outputs the struct’s values without the names of its fields, as shown in the following example: go package main import ( "fmt" ) type Person struct { name string age int email What is the way to get the json field names of this struct ? type example struct { Id int `json:"id"` CreatedAt string `json:"created_at"` Tag string `json:"tag"` Text string `json:"text"` AuthorId int `json:"author_id"` } I try to print the fields with this function : Golang print struct variables on console using 4 different methods. NullInt64 name sql. FieldByName() Function in Golang is used to get the struct field with the given name. or defined types with one of those underlying types (e. Nothing is working. Value and Value. type HasPerson interface { GetPerson() person } func (p person) GetPerson() person { return p } Note the Get in GetPerson here is not to be a "getter" but because you can't have a person in a struct that has a person method. type Vertex struct { X int Y int } func main() { v := Vertex{1, 2} fmt. Mar 6, 2022 · Golang Tutorial Golang: Print Struct. Marshal method struct-in field-i only accepts fields that start with a capital letter. Best. The compiler packs this as a struct with two fields: One pointer to the value and one pointer to a type descriptor. Printf("struct with %d fields)\n", t. There are two ways to print Struct Variables in Golang. Reload to refresh your session. Top or if it doesn't have that, the Name field, or, if the international field is set, skip the Names of those fields should be the values of Request. name); // Prints "Johnny" } The reflect package to loop over all the fields of a struct. Type == 'image'{ fmt. You signed in with another tab or window. I like the answer given here, but I don't like to type, so I'm trying to modify it to return a string using the "%+v" format flag for structs. ; Print fields + field names {FirstName: John LastName: Doe Email: [email protected] When printing the entire struct doesn‘t cut it, we can access individual fields Printing Specific Golang Struct Fields. After typecasting it to string, we can see the fields of the structure along with their names on the console. In Golang, we can print the structure’s fields with their names using the following: Marshal() function of encoding/json package. Standard fmt. – 245K subscribers in the golang community. Like so: &lt;ValueList&gt; &lt;ArraySize&gt;2&lt;/ Aug 14, 2018 · Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Nov 25, 2011 · @magiconair: The capitalization of the first rune determines visibility, is a much more reasonable idea than, "the name of a struct member determines the behavior". This is a good point. We can print structs using Printf function of package fmt along with special tags as arguments to Printf Nov 6, 2017 · Compare structs except one field golang. Another solution is not to store the password at all in the struct. Last updated: 2022-03-08. You can't dereference the string pointer within the struct because then it's no longer accurately described by the struct and you can't dereference the struct because it's not a pointer. 5. Printf("%v\n", data. Value(f)) is the key here. Printf() function of fmt package There are two ways to print Struct Variables in Golang. ] the first character of the identifier's name is a Here is the solution f2. Modified 2 years, 7 months ago. Mar 26, 2015 · You cannot pass a struct to WithFields(). Method 2: %+v for Structs. Method 2: Using go-spew package. I have tried it in many ways and found two possible ways. TypeOf(r). You can use type introspection. Here is my 'Event' model: type Event struct { Event string `json:"Event"` Values Values `json:"Values"` } type Values struct{ Id string `json:"Id"` } You can use type introspection. Type() fieldFmt := "" for i := 0; i < t What you're looking for is struct field annotations for json. Aug 22, 2022 · Struct fields have human readable names in code only (essentially). In the main function, we create a Person instance named p and initialize it with some values. TypeOf(reply) for i := 0; i < t. Go’s fmt package provides a convenient %+v format verb specifically designed for printing structs. This Apr 28, 2020 · Common practice would be to just have the fields be part of the struct. If that makes sense. go This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. Sample script: Go Playground. To print the struct in a more readable format we use the %#v format specifier. In this case I want to know if EmailTemplate. In your first example, the fields are not visible to json. Type descriptor of the struct value, and use Type. It takes Fields type (which is basically map[string]interface{}). 4. You cannot access fields using strings just like you would in a scripting language. TrimSpace, strings. Dec 6, 2019 · If your array (or here slice) contains struct (like Project), you will see their details. Method 2: Using json package. type Test struct { Active bool `json:"active"` Name string `json:"name"` Description string `json:"description"` Amount int `json:"amount"` Currency string `json:"currency"` Type string `json:"type"` } Oct 30, 2022 · Imagine I have these two structs: type Game struct { Name string MultiplayerSupport bool Genre string Version string } type ERP struct { Name string MRPSupport bool SupportedDatabases []string Version string } I want a function attached to these structs that will print the Version variable Oct 1, 2018 · I am new to golang and migrating from php to golang. For example: t := reflect. I know I am missing something here. Sprintf("%#v", var). I now want to see the whole contents of the struct. Next you can add a annotation to the end of the field to tell go what to look for when ast_print_struct_fields. "no returns or refunds" signs Why did the "Western World" shift right in post Covid elections? 80-90s sci-fi movie in which scientists did something to make the world pitch-black because the ozone layer had depleted You can use Elem to dereference the pointer types. Q: What are the benefits of pretty printing a struct in Golang? A: There are several benefits to json. TypeOf(genatt{}) names := make([]string, t. The first way is to use Printf function of package fmt with special tags in the arguments the printing format arguments. Decoder , to omit only the keys you want. In golang, I want to recursively reflect through a struct, getting the name of the field, it's type and the value. Use reflect. This function takes an interface{} value as its argument, which can be any type of data, Using the straightforward fmt. Then this: A field declared with a type but no explicit field name is called an embedded field. Edit: Also worth noting that you don't need to include the struct tags if they are just lowercases of the field names, as the JSON package will match fields that only differ by capitalization (though it prefers exact matches, if there's ambiguity). Age int. Name } fmt. May 5, 2022 · When you call reflect. The FieldByName function in the reflect package in Go (also known as Golang) is used to retrieve the value of a struct field given its name. Printf("%s %s\n", user. Println(user == nil) // will print true Create struct field that is a pointer. golang how to print struct value with pointer. children. Println(names) This will output (try it on the Go Playground): [moving solid outline gradient rotating] when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value. Defining a constraint that "represent[s] all structs with a particular field of a Aug 24, 2018 · var user *User fmt. Interface() So valueValue is of type interface{}. package main import( "fmt" "reflect" ) type Foo struct { Bar string Baz int } var Foo_Bar = reflect. Promoted fields act like ordinary fields Oct 13, 2024 · All public fields, methods and functions starts with uppercase char. package main import ( "fmt" "reflect" ) func main() { type T struct { A int B string } t := T{23 To print out a struct using this function, you’ll need to create a format string that specifies how you want the struct fields displayed. Jun 21, 2024 · I have a struct where I want to implement a String() method for pretty print. type Result struct { ID string `json:"id"` Name string `json:"name"` Test []interface{} `json:"test"` } var result Result json. A struct is similar to the class in the Object-Oriented Programming paradigm. Step 2 − Create a Person struct with two fields: name of type string and age of type int . They may appear complicated, and, well, they are, but once you start using reflection, that's what you end up with. Method 1: Using fmt package. Jan 10, 2023 · How to print structs in Go. x := 5 ptr := reflect. kcvm ltcgqn wvnsqm hudmje tenu ckyni qsc bxzxt zrlj wjbuli