Go - 结构体

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Go 数组允许您定义可以保存几种相同类型的数据项的变量。结构体是 Go 编程中另一种用户定义的数据类型，它允许您组合不同类型的数据项。

结构体用于表示记录。假设您想跟踪图书馆中的书籍。您可能希望跟踪每本书的以下属性：

• 标题
• 作者
• 主题
• 图书 ID

在这种情况下，结构体非常有用。

定义结构体

要定义结构体，必须使用type 和struct 语句。struct 语句定义了一种新的数据类型，其中包含程序的多个成员。type 语句将名称与类型绑定，在本例中类型为 struct。struct 语句的格式如下：

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

一旦定义了结构体类型，就可以使用以下语法声明该类型的变量。

variable_name := structure_variable_type {value1, value2...valuen}

访问结构体成员

要访问结构体的任何成员，我们使用成员访问运算符 (.)。成员访问运算符在结构体变量名和我们希望访问的结构体成员之间编码为一个句点。您将使用struct 关键字定义结构体类型的变量。以下示例说明如何使用结构体：

package main

import "fmt"

type Books struct {
   title string
   author string
   subject string
   book_id int
}
func main() {
   var Book1 Books    /* Declare Book1 of type Book */
   var Book2 Books    /* Declare Book2 of type Book */
 
   /* book 1 specification */
   Book1.title = "Go Programming"
   Book1.author = "Mahesh Kumar"
   Book1.subject = "Go Programming Tutorial"
   Book1.book_id = 6495407

   /* book 2 specification */
   Book2.title = "Telecom Billing"
   Book2.author = "Zara Ali"
   Book2.subject = "Telecom Billing Tutorial"
   Book2.book_id = 6495700
 
   /* print Book1 info */
   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 info */
   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)
}

当编译并执行以上代码时，会产生以下结果：

Book 1 title      : Go Programming
Book 1 author     : Mahesh Kumar
Book 1 subject    : Go Programming Tutorial
Book 1 book_id    : 6495407
Book 2 title      : Telecom Billing
Book 2 author     : Zara Ali
Book 2 subject    : Telecom Billing Tutorial
Book 2 book_id    : 6495700

结构体作为函数参数

您可以像传递任何其他变量或指针一样，将结构体作为函数参数传递。您将以与上述示例相同的方式访问结构体变量：

package main

import "fmt"

type Books struct {
   title string
   author string
   subject string
   book_id int
}
func main() {
   var Book1 Books    /* Declare Book1 of type Book */
   var Book2 Books    /* Declare Book2 of type Book */
 
   /* book 1 specification */
   Book1.title = "Go Programming"
   Book1.author = "Mahesh Kumar"
   Book1.subject = "Go Programming Tutorial"
   Book1.book_id = 6495407

   /* book 2 specification */
   Book2.title = "Telecom Billing"
   Book2.author = "Zara Ali"
   Book2.subject = "Telecom Billing Tutorial"
   Book2.book_id = 6495700
 
   /* print Book1 info */
   printBook(Book1)

   /* print Book2 info */
   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);
}

当编译并执行以上代码时，会产生以下结果：

Book title     : Go Programming
Book author    : Mahesh Kumar
Book subject   : Go Programming Tutorial
Book book_id   : 6495407
Book title     : Telecom Billing
Book author    : Zara Ali
Book subject   : Telecom Billing Tutorial
Book book_id   : 6495700

指向结构体的指针

您可以像定义指向任何其他变量的指针一样，定义指向结构体的指针，如下所示：

var struct_pointer *Books

现在，您可以将结构体变量的地址存储在上面定义的指针变量中。要查找结构体变量的地址，请在结构体名称前放置 & 运算符，如下所示：

struct_pointer = &Book1;

要使用指向该结构体的指针访问结构体的成员，必须使用 "." 运算符，如下所示：

struct_pointer.title;

让我们使用结构体指针重写上述示例：

package main

import "fmt"

type Books struct {
   title string
   author string
   subject string
   book_id int
}
func main() {
   var Book1 Books   /* Declare Book1 of type Book */
   var Book2 Books   /* Declare Book2 of type Book */
 
   /* book 1 specification */
   Book1.title = "Go Programming"
   Book1.author = "Mahesh Kumar"
   Book1.subject = "Go Programming Tutorial"
   Book1.book_id = 6495407

   /* book 2 specification */
   Book2.title = "Telecom Billing"
   Book2.author = "Zara Ali"
   Book2.subject = "Telecom Billing Tutorial"
   Book2.book_id = 6495700
 
   /* print Book1 info */
   printBook(&Book1)

   /* print Book2 info */
   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);
}

当编译并执行以上代码时，会产生以下结果：

Book title     : Go Programming
Book author    : Mahesh Kumar
Book subject   : Go Programming Tutorial
Book book_id   : 6495407
Book title     : Telecom Billing
Book author    : Zara Ali
Book subject   : Telecom Billing Tutorial
Book book_id   : 6495700