Golang print struct field names. Structs can either be named or anonymous.
Golang print struct field names The format 'verbs' are derived from C's but are simpler. Jun 14, 2023 · Overview GO struct is named collection of data fields which can be of different types. Printf("%v", myVar) From the fmt package's documentation page: %v the value in a default format. Nov 29, 2016 · 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"` Struct Printing Basics Introduction to Structs in Go In Go programming, structs are fundamental data structures that allow you to create custom types by combining different data fields. Oct 15, 2015 · How to print struct with String () of fields? Asked 9 years, 8 months ago Modified 8 years, 8 months ago Viewed 2k times May 3, 2020 · The reflect. fmt. Apr 27, 2023 · I have written a program to retrieve the names of fields inside a struct, and it works perfectly fine. Jul 12, 2025 · A structure or struct in Golang is a user-defined type that allows to group/combine items of possibly different types into a single type. My goal is to pass an object of any struct type and then to parse all field to get name… @xgz123 you're probably calling reflect. type Student struct { id int name string Struct Literals A struct literal denotes a newly allocated struct value by listing the values of its fields. Generally, each field definition is composed of a name and a type. However, the Author field shows only the pointer address - Author:0xc0000900c0, not its content. The Printf() function 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. I don't know of a more general solution though. Defining a struct You create a new struct by using the type and struct keywords, and explicitly define the name and type of the fields. To print struct variables in Go, you can use the following methods: Use fmt. Covers initialization, nested structs, and best practices for struct usage. FieldByName () Function in Golang is used to get the struct field with the given name. Jul 23, 2025 · A struct in Go is a composite data type that groups variables (fields) under a single name. Jan 1, 2020 · Structs are a way to structure and use data. However, that notation is cumbersome, so the language permits us instead to write just p. Jul 12, 2025 · One interface is having get_name method which will return names of course and contest. In this tutorial, we will cover how to create and perform basic CRUD (Create, Read, Update, Delete) operations on arrays of structs with Feb 1, 2025 · Not sure how to structure your Go web application? My new book guides you through the start-to-finish build of a real world web application in Go — covering topics like how to structure your code, manage dependencies, create dynamic database-driven pages, and how to authenticate and authorize users securely. org/p/D0KwGP6Cxa0) currently produces the following output: Print Golang structure fields with names using `Marshal` from `encoding/json` or `Printf` from `fmt` with `%+v` argument. Nov 5, 2025 · FieldByName and related functions consider struct field names to be equal if the names are equal, even if they are unexported names originating in different packages. We then create an inner struct to get the ResourceType in our custom UnmarshalJSON method, so that we can have a switch statement to decide which struct we want our go program to decode into depending on the resource type. It has a field named field_name1 of type field_type1 and a field named field_name2 of type field_type2. So far I have: type MultiQuestions struct { QuestionId int64 QuestionType string QuestionText s Dec 30, 2024 · Mastering Structs and Interfaces in Go Go (often referred to as Golang) is a statically typed, compiled programming language designed and developed by Google. Aug 10, 2018 · Note 2 - Change the JSON key in the output by using a struct field tag. Feb 28, 2025 · Often, you may need to print struct variables for debugging or logging purposes. Why Use Pointers with Structs? Using Struct Fields Struct fields are accessed using a dot. Structs can either be named or anonymous. Jul 12, 2025 · In Go, structs are used to create custom data types that group different fields together. Time type Salary of int type . These variables can be of different types, which allows you to represent real-world entities more effectively. Eg. We also embedded another Address struct to represent related user address data. This will print the struct in a format that includes the struct’s name, field names, and values. Printf() with format “verbs” %+v or %#v. To access this function, one needs to imports the reflect package in the program. type Programmer struct { FirstName string LastName string Language string `help:"The primary programming language used by the programmer"` } On another note, having taken a second look at your data, I think you could benefit from using interfaces to best represent the different types. Go offers struct tags which are discoverable via reflection. Sep 26, 2014 · fmt. What's wrong with passing the struct? If you don't pass the struct, how do you intend to get the type? Jul 24, 2024 · Working with Structs: Inspecting Fields and Methods Working with structs using reflection is a powerful way to dynamically interact with the fields and methods of struct types. Structs Consider the example of a laptop. Print using Marshal of package encoding/json. I'm on mobile, but to give a trivial example. Understanding how to print and format structs is crucial for debugging and displaying data effectively. Example: Nov 5, 2025 · an anonymous struct field is handled as if the fields of its value were part of the outer struct. We can do this with the help of package fmt which implements formatted I/O with functions analogous to C's printf and scanf. In Go, we can represent a laptop using a struct like this: type Each unnamed struct type literal starts with a struct keyword which is followed by a sequence of field definitions enclosed in a {}. https://go. This guide will help you rank 1 on Google for the keyword golang pretty print struct. Here’s how you can inspect a struct’s fields and methods: Inspecting Fields: Aug 5, 2014 · I want to return the name of a struct attribute using the reflect package. You can list just a subset of fields by using the Name: syntax. Syntax: type Mar 4, 2016 · I found this question with this great answers: How to find a type of a object in Golang? I played around with the answer and tried to get the name of a struct in the same way: package main impo Feb 7, 2024 · How to Print Struct Values in Go Printing struct values is a common requirement for debugging in Go. Jul 12, 2025 · There are two ways to print struct variables on the console as follows: 1. Dec 17, 2020 · In order to extract the value of an XML field, the chardata annotation is needed. Explore event-driven architecture in Golang to decouple microservices, enable real-time interactions, and convert synchronous mechanisms into asynchronous communication with practical examples. You can get that as a string with format!("{:?}", my_struct). Convert the struct to JSON and print the output. Initializing Structs Structs can be initialized in several ways, including using field names or positional syntax. Jul 12, 2025 · Suppose, we need to print the structure with its fields corresponding value. Using the straightforward fmt. Here’s how you can inspect a struct’s fields and methods: Inspecting Fields: Dec 30, 2024 · Mastering Structs and Interfaces in Go Go (often referred to as Golang) is a statically typed, compiled programming language designed and developed by Google. Apr 14, 2022 · We will be understanding the basics of operating on structs like declaration, initialization and adding functional logic into those structs. Apr 14, 2025 · Golang Structs — A Complete Guide Structs Structs in Golang are a compound data type that group different fields under the same name. It’s simple but doesn’t show the field names, which can sometimes make the output hard to interpret. Q: What are the benefits of pretty printing a struct in Golang? In Go (Golang), a "Print Struct" refers to the practice of outputting the contents of a struct type to the console or standard output for debugging or logging purposes. FieldByName (name string) (reflect. Understanding these constructs and patterns is key for building robust software solutions. Employee can have Name of string type Age of int type DOB of time. Go allows fields of a struct to be decorated with a tag, these can be read by packages operating on the struct and change the way they are treated. Using the Printf function with the following tags. This is a great way to make your code more flexible and easier to work with. What is Reflection? Reflection is a programming concept that derives from Meta-Programming. Jun 14, 2020 · In the above format, struct_name is the name of the struct. Printf package and add the flag (%+v). This flag adds field names Code example on printing a struct in go (golang) After typecasting it to string, we can see the fields of the structure along with their names on the console. Key Points: Clarity: It explicitly shows the field names alongside their values, making the output easier to understand, especially for larger structs with numerous fields. The first anonymous field is "promoted", which means any field you access on the struct "passes through" to the promoted anonymous field. Anybody know if this function exists, or its something that needs to be implemented? Learn how to create a Golang slice of structs with this detailed tutorial. A pointer to a struct allows you to directly reference and modify the data in the original struct without making a copy. For example, different attributes are used to represent an employee in an organization. Jan 21, 2023 · The below example golang code defines a struct Person with fields that match the structure of the YAML data. X. Nov 2, 2021 · For a type without fields, #[derive(Debug)] will just print the type name. Jul 15, 2025 · 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. That way if I change the fields in the struct the menu will update automatically without having to go back and manually Golang Pretty Print Struct Learn how to pretty print struct in Golang with a simple example. StructOf () Function in Golang is used to get the struct type containing fields. when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value Here is an example: Sep 26, 2014 · fmt. Following the same process a Struct is created with a name and a Value field, which will be the text inside the brackets. A laptop can have various components such as CPU, RAM, storage, and a manufacturer. < 3/27 > And bufio also implements a buffered reader/writer, which it does by combining a reader and a writer into one struct using embedding: it lists the types within the struct but does not give them field names. See the example below and compare these three options. X to a single machine instruction, whereas a dynamic lookup will need some sort of hash table implementation or similar). So why is this linter warning me about these names? May 21, 2019 · I am unmarshaling a struct and I would like it to print it in a formatted manner. The key is an identifier for the tag, and value is a string that contains the metadata we want to associate May 24, 2016 · 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. Use external packages to pretty-print structs, for example, go-spew. You could also reference each value in the format which is a struct. In this blog post, we’ll explore 5 different ways to print struct variables in Go with examples. Rank 1 on Google for 'golang slice of structs'. Print() does not print variable names of Go structs, but it does not mean you cannot do that. When you initialize a variable with a new struct, it’s as though you’ve photocopied a form and made it ready to fill out. This is as expected since *Author is a pointer type, and its value is the address. The number of fields of a struct type can be zero. golang. Jan 25, 2022 · I'm not very expert of GoLang, but I need to run troubleshooting on a project. A struct in Go is a composite data type that groups together variables (fields) under a single name, allowing developers to create complex data structures. Learn how to define structs, initialize arrays, access elements, and modify data efficiently. One of Go’s most notable features @xgz123 you're probably calling reflect. The function takes a single argument, which is a string representing the name of the field to retrieve. You will learn how to use the Go struct including defining a struct, accessing and modifying fields, and passing a struct to a function. (And the order of named fields is irrelevant. Mar 11, 2025 · This tutorial provides a comprehensive guide on creating and using an array of structs in Golang. Jul 24, 2024 · Working with Structs: Inspecting Fields and Methods Working with structs using reflection is a powerful way to dynamically interact with the fields and methods of struct types. Is there a way to print the string value of a enum field? Go – Array of Structs Arrays in Go are fixed-size collections of elements of the same type. Includes examples and code snippets. It prints the struct’s field names along with their values. Print Struct with field names in Golang? GitHub Gist: instantly share code, notes, and snippets. It is also possible to create nested structs in Go. This tutorial explores various techniques for displaying struct information clearly and efficiently. The name of a field must be unique within the struct. Jan 31, 2024 · } Output: {ID:1 Title:How to Print a Structure in Golang Author:0xc0000900c0 Content:This is a blog post} This code prints all field values of the article structure. Whether you're debugging, logging, or simply need to understand your data structure, knowing how to print structs properly can significantly improve your code's struct field ApiEndpoint should be APIEndpoint struct field ApiVersion should be APIVersion I did some Googling and I can not find any requirements for struct field names regarding this. Dec 16, 2019 · In order to be able to use a struct and its fields outside of the Go package where the struct type is defined, both the struct name and the desired field names must begin with an uppercase letter. In this guide, learn how to work with JSON in Go using the encoding/json package. Learn reflection by coding a SQL query generator in Go. Hi gophers, I'm new to golang so apologies in advance if this is a dumb question, but how do you iterate through nested structs and print the fields… Nov 26, 2024 · This is particularly useful when working with structs and interfaces to implement dynamic behavior without knowing types at compile time. StructField: gets the field at position ‘i’ in a struct. Structs in Golang Structs or Structures in Golang are the sequences or collections of built-in data types as a single type interface. TypeOf (struct) rather than reflect. Ask questions and post articles about the Go programming language and related tools, events etc. Field () Function in Golang is used to get the i'th field of the struct v. X, without the explicit dereference. For example json view for the client without a sensitive field, and json view for the database WITH the sensitive field. Within the definition of the struct, we define the JSON tags that map the fields of our structs directly to the fields in our marshaled JSON. Example: Jun 10, 2022 · How to represent Golang struct with variable field names [duplicate] Asked 2 years, 10 months ago Modified 2 years, 10 months ago Viewed 2k times There are two things going on. Any real-world entity which has some set of properties/fields can be represented as a struct. When working with structs, using pointers can be especially beneficial for managing memory efficiently and for avoiding unnecessary copying of data. I know Go reflections is helpful, but the issue is getting and setting the values requires knowing the types, if you want to use something like SetInt. Sep 15, 2023 · Go’s fmt package provides a convenient %+v format verb specifically designed for printing structs. My code (https://play. To create a new struct, you must first give Go a blueprint that describes the fields the struct contains. Struct acts as a container that has different heterogeneous data types which together represents an entity. Implementing the Stringer interface is the surest way to always get what you want. when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value Here is an example: Apr 18, 2023 · Defining Structures in Golang To define a structure in Golang, you use the struct keyword, followed by a list of field names and their respective data types, enclosed in curly braces. Println () function can also be used to print a struct. Unexported fields begin with a lowercase letter and are meant to be inaccessible outside the package they are Nov 23, 2023 · Golang Technique: Custom Struct Tag Like `json:"name"` Do you know the json:"name" tag in Go? You can actually create your own custom struct tags, just like it. Printing The verbs: General: %v the value in a default format when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value (floating-point infinities and NaNs print as ±Inf and NaN) %T a Go-syntax Feb 2, 2024 · The reflect package equips developers with functions and types to introspect and manipulate variables dynamically, allowing operations like inspecting field names and values within a struct. Consider a scenario where a generic approach is required to convert any given struct to a string without prior knowledge of its fields. a field implementing Marshaler is written by calling its MarshalXML method. The field values are set Jan 12, 2023 · All we have to do is to add %+v to our print function. dev Apr 11, 2024 · Learn how to define and use structs in Go. Jun 13, 2020 · Field name will not be printed. Example package main // importing necessary packages import ( Dec 10, 2020 · I need to print all form requests to log, for later debugging. This is the default way of printing a struct. This shows both concepts: Jun 26, 2013 · A possible drawback of delete is that you sometimes might want to support multiple json views of your struct (map). Then you can use standard JSON encode when returning the full struct, and mapstructure when returning a partial list of field (you encode into a map and then iterate over the map to return the required fields). Example 1: This program will take 2 inputs. Oct 15, 2024 · Printing the Entire Struct If you want to print the entire struct and include its field names automatically, you can use a special verb to do so: Mar 7, 2024 · The output is: {X:1 Y:2}. And this allows you to initialize only a subset of fields. ) type SomeFormInput { Apr 6, 2017 · 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. Jun 10, 2022 · How to represent Golang struct with variable field names [duplicate] Asked 2 years, 10 months ago Modified 2 years, 10 months ago Viewed 2k times Nov 5, 2024 · In Golang, structures (or structs) allow us to group elements of various types into a single unit, which is useful for modeling real-world entities. Calling Field (i) on a Type returns a StructField which doesn't have the Interface method. Calling Field(i) on a Type returns a StructField which doesn't have the Interface method. In order to understand reflection in Go, it’s going to be useful for us to see what meta-programming and reflection is in general. We then create an instance of Person, set its fields, and print it. Syntax: func (v Value) Field(i int) Value Parameters Jul 16, 2016 · Structs in Golang represent one of the most common variable types and used practically everywhere, from dealing with configuration options to marshaling of JSON or XML documents using encoding/json or encoding/xml packages. %+v – It will print both field and value. A I'm looking for something like PHP's print_r or python's dict. May 19, 2021 · 4 I want to be able to extract the FIELD names (not the values) of a struct as strings, put them in a slice of strings and then use the names to print in a menu in Raylib (a graphics library for Go) elsewhere in a program. Apr 4, 2023 · In this Golang article, we will write programs to print struct variables. Jun 3, 2017 · 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. Anonymous structures are unnamed, temporary structures used for a one-time purpose, while anonymous fields allow embedding fields without names. StructField, bool): Finds a field in the struct by its name and tells you if it exists or not. ) The special prefix & returns a pointer to the struct value. 245K subscribers in the golang community. It's inefficient compared to direct access (the compiler knows the offset of the X field in a Vertex structure, it can compile v. 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. Now I'm try to print the value of same variables, but I receive as output the address and not the value: attrs := core. Fortunately it is still possible to use the struct -- just have a look at my answer. . Dec 25, 2024 · "fmt" "reflect" ) // Programmer represents a programmer with first name, last name, and their primary programming language. Dec 27, 2023 · Here we define a User struct with some core fields like first/last name, email, and age. Dec 27, 2023 · What Are Struct Tags? A struct tag is an optional string literal that can be added to a field in a struct declaration. Go also supports the name: value syntax for initializing a struct (the order of fields is irrelevant when using this syntax). ValueOf(struct). Dec 14, 2024 · Iterating through Struct Fields in Go So, you’re working with structs in Go, and the inevitable question hits you: How do I loop through the fields of this thing without breaking my head? Relax Nov 5, 2025 · Package fmt implements formatted I/O with functions analogous to C's printf and scanf. Field tags are part of the struct's field definition and allow nice and easy way to store meta data about fields for many use cases (field mapping, data validation, ORM Sep 21, 2013 · When writing code that reflects over a struct type, it's a common requirement to know the full set of struct fields, including fields available due to embedding of anonymous members while excluding fields that are erased because they're at the same level as another field with the same name. For anonymous fields, the field name you can use is the name of the type. Nov 24, 2024 · By using slices in conjunction with structs, you can handle complex data scenarios efficiently and effectively in Go. Note that I specifically want to employ something that reads a mutable struct field-variable _name_ (maybe like this?), a field name that is compile-time managed, vs employing a map/hash whose "keyname" (again: I'm a newbie Rustacean) is run-time assigned and therefore less dependable for other code use/reference/lookups. This concept is generally compared with the classes in object-oriented programming. It allows us to group data. Println prints the struct in this barebones format. The reflect. I need to have something like this, where formInput are different kind of structs. Nov 5, 2024 · In Golang, structures (or structs) allow us to group elements of various types into a single unit, which is useful for modeling real-world entities. and so on. Dec 14, 2024 · By default, fmt. Apr 28, 2020 · The reflect. A third variation is %+v which will include the field names, but not the struct type. an anonymous struct field of interface type is treated the same as having that type as its name, rather than being anonymous. Mar 5, 2023 · In this example we define a Customer struct which has a field - Name and a Payment struct which has a field - Amount. Jul 12, 2025 · Always pass the field values in the same order in which they are declared in the struct. The yaml struct tags are used to indicate the corresponding field names in YAML. For example: type User struct { ID int `json:"id"` Name string `json:"name"` email string `json:"email"` } Here we‘ve added tags to each field in the form key:"value". Apr 26, 2022 · Golang Reflection ExampleGo (Golang) Reflection’s is a powerful feature that allows us to bypass the Go type system and do very interesting things. %#v – It will print the struct name, also both field and value. Some key notes on struct declaration anatomy: Aug 20, 2021 · Standard fmt. 2. Using %+v simplifies the process and is especially useful for debugging because it displays both field names and values. In this article, we will see how to declare and use it. 1. For example If you declare the same enum inside a struct and print the struct using "%v", it will print enum's numeric value. Jun 4, 2020 · Try it As you can see “%+v” verb will print the struct with the field names and structs. These enjoy a wide range of use in the standard library in the JSON/XML and other encoding packages. It's also inhibits static typing: the compiler has no way to check that you're not trying Sep 8, 2025 · A struct is a user defined data type which represents a collections of fields. Jan 14, 2025 · golang gopher In Go, struct fields can be private (unexported) or public (exported). May 20, 2021 · Reflection is the ability of a program to inspect its own values and variables at run time and find their type. In this article, we will explore using reflection with structs and interfaces in Go. 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. Example: Dec 25, 2022 · %v the value in a default format when printing structs, the plus flag (%+v) adds field names %#v a Go-syntax representation of the value %T a Go-syntax representation of the type of the value %% a literal percent sign; consumes no value Here's an example of using Printf() with %v verb to print out the struct: Learn how to pretty print struct in Golang with this step-by-step guide. Oct 24, 2019 · Similarly, structs collect different pieces of data together and organize them under different field names. However, when it comes to a pointer of struct inside a struct, it doesn't work. ValueOf (struct). Golang noob question: Why can I not use the "%+v" flag for a struct in the String () implementation method? I have a struct where I want to implement a String() method for pretty print. @xgz123 you're probably calling reflect. In some cases you’ll also want to print the field types, in that case you can use the “%#v” verb. To access the field X of a struct when we have the struct pointer p we could write (*p). The most I've found is that if you want to make a field public you have to capitalize it. Take a look! Nov 16, 2023 · Field (i int) 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. Here, there is no concept of classes, instead of that structs are used to represent a collection of related fields or properties. Metaprogramming is a Sep 17, 2021 · As the Go programming language achieves more popularity on the frontend, learn how to solve code issues using reflection in this tutorial. Using Name of the Field and Shorthand Declaration in the Main Function In this method, we will create a child struct and further create two fields name and age in it. Also, this concept is generally compared with the classes in object-oriented programming. You can also get fields by name. Second is the "promoted" field. Pointers to structs Struct fields can be accessed through a struct pointer. TypeOf(struct) rather than reflect. Also, you can’t initialize only a subset of fields with the above syntax. Println() method outputs the struct’s values without the names of its fields, as shown in the following example: go Introduction In Golang programming, effectively printing struct contents is a fundamental skill that every developer needs to master. First is anonymous fields. How to recursively print all fields of structs using reflect? I'm trying to learn more about reflect package and currently i'm stuck at iterating all (including embedded) struct fields. A struct has different fields of the same or different data types and is declared by composing a fixed set of unique fields. Basic Struct Definition and Printing When working with structs, the most straightforward way to print them Sep 21, 2013 · Most code shouldn't need this sort of dynamic lookup. I won't do all the methods but you get the idea type Feb 2, 2024 · Convert Nested Structs to JSON in Go Let’s define a more complex struct with nested struct. What if I need to know all the fields available to me? Nov 25, 2024 · In this example, we define a struct named Person with two fields: Name of type string and Age of type int. // The 'language' field includes a struct tag that provides additional metadata. Hi guys, I'm in trouble, can't make my code running properly. An array of structs is a collection where each element is a struct, allowing you to group and store multiple related fields for each element in a structured way. May 2, 2013 · 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. They are similar to structs in C and to classes in oriented … About Structs In Go, a struct is a sequence of named elements called fields, each field has a name and type. Perfect for beginners and experienced developers looking to enhance their Golang skills. With the help of the interface, we will access the structure’s variable as we don't want to access the structure's variable from outside. Oct 5, 2016 · How do I know the fields I can access from the reply object/interface? I tried reflection but it seems you have to know the field name first. (All defined in my code. type Disorder interface { // methods that all disorders should have Name() string Duration() uint Severity () uint } // now disorder A can satisfy it. %v the value in a default format %+v the plus flag adds field names %#v a Go-syntax representation of the value. Nov 17, 2021 · JSON is one of the most-used formats for storing data. They are all documented at the top of the fmt documentation. I know how to do this by hard-coding the field names, but I want a function that works even if I change the Person struct. Structs can be compared with classes in the Object-Oriented Programming paradigm. cecyifqjyllpokuprefggvoqzotpsysmpeauscxmyytodzctexttnbvrlypwkirmjvcjhya