Go language structs

In Go, arrays can store data of the same type, but in structs we can define different data types for different items.

A struct is a data collection composed of a series of data of the same type or different types.

A struct represents a record, such as saving library book records. Each book has the following properties:

Title: Title
Author: Author
Subject: Subject
ID: Book ID

Define struct

Defining a struct requires the type and struct statements. The struct statement defines a new data type, and the struct has one or more members. The type statement sets the name of the struct. The format of a struct is as follows:

type struct_variable_type struct {
   member definition
   member definition
   ...
   member definition
}

Once a struct type is defined, it can be used for variable declarations. The syntax format is as follows:

variable_name := structure_variable_type {value1, value2...valuen}
或
variable_name := structure_variable_type { key1: value1, key2: value2..., keyn: valuen}

Example as follows:

Example

package main

import "fmt"

type Books struct {
title string
author string
subject string
book_id int
}

func main() {

// Create a new struct
fmt.Println(Books{"Go language", "www.example.com", "Go language tutorial", 6495407})

// You can also use the key => value format
fmt.Println(Books{title: "Go language", author: "www.example.com", subject: "Go language tutorial", book_id: 6495407})

// Ignored fields are 0 or empty
fmt.Println(Books{title: "Go language", author: "www.example.com"})
}

The output result is:

{Go 语言 www.example.com Go 语言教程 6495407}
{Go 语言 www.example.com Go 语言教程 6495407}
{Go 语言 www.example.com  0}

Accessing struct members

To access struct members, you need to use the dot (.) operator..Operator, in the format:

struct.member name

Struct type variables are defined using the struct keyword, as in the following example:

Example

package main

import "fmt"

type Books struct {
title string
author string
subject string
book_id int
}

func main() {
var Book1 Books /* Declare Book1 as Books type */
var Book2 Books /* Declare Book2 as Books type */

/* Description of book 1 */
Book1.title = "Go language"
Book1.author = "www.example.com"
Book1.subject = "Go language tutorial"
Book1.book_id = 6495407

/* Description of book 2 */
Book2.title = Python Tutorial
Book2.author = "www.example.com"
Book2.subject = Python Language Tutorial
Book2.book_id = 6495700

/* Print Book1 information */
fmt.Printf( "Book 1 title : %s\n", Book1.title)
fmt.Printf( "Book 1 author : %s\n", Book1.author)
fmt.Printf( "Book 1 subject : %s\n", Book1.subject)
fmt.Printf( "Book 1 book_id : %d\n", Book1.book_id)

/* Print Book2 information */
fmt.Printf( "Book 2 title : %s\n", Book2.title)
fmt.Printf( "Book 2 author : %s\n", Book2.author)
fmt.Printf( "Book 2 subject : %s\n", Book2.subject)
fmt.Printf( "Book 2 book_id : %d\n", Book2.book_id)
}

The execution result of the above example is:

Book 1 title : Go 语言
Book 1 author : www.example.com
Book 1 subject : Go 语言教程
Book 1 book_id : 6495407
Book 2 title : Python 教程
Book 2 author : www.example.com
Book 2 subject : Python 语言教程
Book 2 book_id : 6495700

Structs as function parameters

You can pass a struct type as a parameter to a function just like other data types, and access the struct variables in the manner of the above examples:

Example

package main

import "fmt"

type Books struct {
title string
author string
subject string
book_id int
}

func main() {
var Book1 Books /* Declare Book1 as Books type */
var Book2 Books /* Declare Book2 as Books type */

/* Description of book 1 */
Book1.title = "Go language"
Book1.author = "www.example.com"
Book1.subject = "Go language tutorial"
Book1.book_id = 6495407

/* Description of book 2 */
Book2.title = Python Tutorial
Book2.author = "www.example.com"
Book2.subject = Python Language Tutorial
Book2.book_id = 6495700

/* Print Book1 information */
printBook(Book1)

/* Print Book2 information */
printBook(Book2)
}

func printBook( book Books ) {
fmt.Printf( "Book title : %s\n", book.title)
fmt.Printf( "Book author : %s\n", book.author)
fmt.Printf( "Book subject : %s\n", book.subject)
fmt.Printf( "Book book_id : %d\n", book.book_id)
}

The execution result of the above example is:

Book title : Go 语言
Book author : www.example.com
Book subject : Go 语言教程
Book book_id : 6495407
Book title : Python 教程
Book author : www.example.com
Book subject : Python 语言教程
Book book_id : 6495700

struct pointer

You can define a pointer to a struct similarly to other pointer variables. The format is as follows:

var struct_pointer *Books

The pointer variable defined above can store the address of a struct variable. To view the address of a struct variable, you can place the & symbol before the struct variable:

struct_pointer = &Book1

Use the "." operator to access struct members via a struct pointer:

struct_pointer.title

Next, let's use a struct pointer to rewrite the above example, the code is as follows:

Example

package main

import "fmt"

type Books struct {
title string
author string
subject string
book_id int
}

func main() {
var Book1 Books /* Declare Book1 as Books type */
var Book2 Books /* Declare Book2 as Books type */

/* Description of book 1 */
Book1.title = "Go language"
Book1.author = "www.example.com"
Book1.subject = "Go language tutorial"
Book1.book_id = 6495407

/* Description of book 2 */
Book2.title = Python Tutorial
Book2.author = "www.example.com"
Book2.subject = Python Language Tutorial
Book2.book_id = 6495700

/* Print Book1 information */
printBook(&Book1)

/* Print Book2 information */
printBook(&Book2)
}
func printBook( book *Books ) {
fmt.Printf( "Book title : %s\n", book.title)
fmt.Printf( "Book author : %s\n", book.author)
fmt.Printf( "Book subject : %s\n", book.subject)
fmt.Printf( "Book book_id : %d\n", book.book_id)
}

The execution result of the above example is:

Book title : Go 语言
Book author : www.example.com
Book subject : Go 语言教程
Book book_id : 6495407
Book title : Python 教程
Book author : www.example.com
Book subject : Python 语言教程
Book book_id : 6495700

other extensions