Go語言結構體

Go數組允許定義一種可以保存多個相同類型的數據項的變量類型，但結構體是Go編程中可用的另一個用戶定義的數據類型，它允許組合不同類型的數據項。

結構體用於表示記錄，假設想在圖書館中跟蹤圖書。可能希望跟蹤每本圖書的以下屬性：

• 標題(Title)
• 作者(Author)
• 科目(Subject)
• 圖書編號(Book ID)

定義結構體

要定義結構，必須使用type和struct語句。struct語句定義了一個新的數據類型，在程序中有多個成員。type語句在例子中綁定一個類型爲struct的名字。 struct語句的格式如下：

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

當定義了結構體類型，它可以用於使用以下語法聲明該類型的變量。

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

訪問結構體成員

要訪問結構的任何成員，可使用成員訪問運算符(.)。成員訪問運算符被編碼爲結構變量名稱和希望訪問的結構成員的名稱。使用struct關鍵字定義結構類型的變量。以下是解釋結構用法的示例：

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 */
   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)
}

當上述代碼編譯和執行時，它產生以下結果：

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

結構體作爲函數參數

可以傳遞一個結構體作爲一個函數參數，與傳遞其他變量或指針的方式非常相似。可以使用類似於上面示例中訪問的方式來訪問結構變量：

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);
}

當上述代碼編譯和執行時，它產生以下結果：

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

指針指向結構

可以以非常類似於定義指向其他變量的指針的方式來定義結構的指針，如下所示：

var struct_pointer *Books

現在，可以在上面定義的指針變量中存儲結構體變量的地址。要查找結構體變量的地址，將&操作符放在結構體名稱之前，如下：

struct_pointer = &Book1;

要使用指向該結構體的指針來訪問結構的成員，必須使用「.」。 運算符如下：

struct_pointer.title;

現在，重寫上面的例子使用結構指針，希望這能讓您更容易地理解這個概念，代碼如下：

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);
}

當上述代碼編譯和執行時，它產生以下結果：

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