结构（ Structures）

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2023-12-01

Go数组允许您定义可以包含多个相同类型的数据项的变量。 Structure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。

结构用于表示记录。假设您想要跟踪库中的书籍。您可能希望跟踪每本书的以下属性 -

Title
Author
Subject
Book ID

在这种情况下，结构非常有用。

定义一个结构 (Defining a Structure)

要定义结构，必须使用type和struct语句。 struct语句定义了一个新的数据类型，为您的程序提供了多个成员。 type语句使用我们的case中的struct类型绑定一个名称。 struct语句的格式如下 -

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

定义结构类型后，可以使用以下语法声明该类型的变量。

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

访问结构成员 (Accessing Structure Members)

要访问结构的任何成员，我们使用member access operator (.). 成员访问运算符被编码为结构变量名称和我们希望访问的结构成员之间的句点。您可以使用struct关键字来定义结构类型的变量。以下示例说明如何使用结构 -

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)
}

编译并执行上述代码时，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

作为函数参数的结构 (Structures as Function Arguments)

您可以将结构作为函数参数传递，与传递任何其他变量或指针的方式非常相似。您将以与上例中相同的方式访问结构变量 -

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);
}

编译并执行上述代码时，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

指向结构的指针

您可以使用与定义指向任何其他变量的指针相同的方式定义指向结构的指针，如下所示 -

var struct_pointer *Books

现在，您可以将结构变量的地址存储在上面定义的指针变量中。要查找结构变量的地址，请将＆运算符放在结构名称之前，如下所示 -

struct_pointer = &Book1;

要使用指向该结构的指针访问结构的成员，必须使用“。”。运算符如下 -

struct_pointer.title;

让我们使用结构指针重写上面的例子 -

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);
}

编译并执行上述代码时，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