D編程 結(jié)構(gòu)(Structs)

結(jié)構(gòu)Structs用于表示記錄，假設(shè)您想跟蹤圖書館中的書籍，您可能需要跟蹤有關(guān)每本書的以下屬性-

• 標題 title
• 作者 author
• 主題 subject
• 圖書ID book_id

定義結(jié)構(gòu)

要定義結(jié)構(gòu)，必須使用 struct 語句， struct語句定義了一種新的數(shù)據(jù)類型， struct語句的格式如下:

struct [structure tag] { 
   member definition; 
   member definition; 
   ... 
   member definition; 
} [one or more structure variables]; 

結(jié)構(gòu)標簽tag是可選的，每個成員定義都是一個普通的變量定義，如int i；或浮動f，在分號前面的結(jié)構(gòu)定義末尾，您可以指定一個或多個可選的結(jié)構(gòu)變量。這是聲明Books結(jié)構(gòu)的方式-

struct Books {
   char [] title;
   char [] author;
   char [] subject;
   int   book_id;
};

訪問結(jié)構(gòu)

要訪問結(jié)構(gòu)的任何成員，請使用成員訪問運算符(.)，成員訪問運算符被編碼為結(jié)構(gòu)變量名和我們希望訪問的結(jié)構(gòu)成員之間的句號，您可以使用 struct 關(guān)鍵字定義結(jié)構(gòu)類型的變量。

import std.stdio; 
 
struct Books { 
   char [] title; 
   char [] author; 
   char [] subject; 
   int   book_id; 
}; 
 
void main( ) { 
   Books Book1;        /* Declare Book1 of type Book */
   Books Book2;        /* Declare Book2 of type Book */
   
   /* book 1 specification */
   Book1.title="D Programming".dup; 
   Book1.author="Raj".dup; 
   Book1.subject="D Programming Tutorial".dup;
   Book1.book_id=6495407; 
   
   /* book 2 specification */
   Book2.title="D Programming".dup; 
   Book2.author="Raj".dup; 
   Book2.subject="D Programming Tutorial".dup; 
   Book2.book_id=6495700; 
   
   /* print Book1 info */
   writeln( "Book 1 title : ", Book1.title); 
   writeln( "Book 1 author : ", Book1.author); 
   writeln( "Book 1 subject : ", Book1.subject); 
   writeln( "Book 1 book_id : ", Book1.book_id);  
   
   /* print Book2 info */
   writeln( "Book 2 title : ", Book2.title); 
   writeln( "Book 2 author : ", Book2.author); 
   writeln( "Book 2 subject : ", Book2.subject); 
   writeln( "Book 2 book_id : ", Book2.book_id); 
}

編譯并執(zhí)行上述代碼后，將產(chǎn)生以下輸出-

Book 1 title : D Programming 
Book 1 author : Raj 
Book 1 subject : D Programming Tutorial 
Book 1 book_id : 6495407 
Book 2 title : D Programming 
Book 2 author : Raj 
Book 2 subject : D Programming Tutorial 
Book 2 book_id : 6495700

結(jié)構(gòu)參數(shù)

您可以通過與傳遞任何其他變量或指針非常相似的方式將結(jié)構(gòu)作為函數(shù)參數(shù)傳遞，您將以與上述示例相同的方式訪問結(jié)構(gòu)變量-

import std.stdio;

struct Books { 
   char [] title; 
   char [] author; 
   char [] subject; 
   int   book_id; 
}; 
 
void main( ) { 
   Books Book1;        /* Declare Book1 of type Book */
   Books Book2;        /* Declare Book2 of type Book */
   
   /* book 1 specification */
   Book1.title="D Programming".dup; 
   Book1.author="Raj".dup; 
   Book1.subject="D Programming Tutorial".dup; 
   Book1.book_id=6495407;  
   
   /* book 2 specification */
   Book2.title="D Programming".dup; 
   Book2.author="Raj".dup; 
   Book2.subject="D Programming Tutorial".dup; 
   Book2.book_id=6495700;  
   
   /* print Book1 info */
   printBook( Book1 );  
   
   /* Print Book2 info */
   printBook( Book2 );  
}
 
void printBook( Books book ) { 
   writeln( "Book title : ", book.title); 
   writeln( "Book author : ", book.author); 
   writeln( "Book subject : ", book.subject); 
   writeln( "Book book_id : ", book.book_id); 
}

編譯并執(zhí)行上述代碼后，將產(chǎn)生以下輸出-

Book title : D Programming 
Book author : Raj 
Book subject : D Programming Tutorial 
Book book_id : 6495407 
Book title : D Programming 
Book author : Raj
Book subject : D Programming Tutorial 
Book book_id : 6495700 

結(jié)構(gòu)初始化

可以用兩種形式初始化結(jié)構(gòu)，一種使用構(gòu)造函數(shù)，另一種使用{}格式。一個如下所示。

import std.stdio;

struct Books { 
   char [] title; 
   char [] subject="Empty".dup; 
   int   book_id=-1; 
   char [] author="Raj".dup;  
}; 
 
void main( ) { 
   Books Book1=Books("D Programming".dup, "D Programming Tutorial".dup, 6495407 ); 
   printBook( Book1 ); 
   
   Books Book2=Books("D Programming".dup, 
      "D Programming Tutorial".dup, 6495407,"Raj".dup ); 
   printBook( Book2 );
   
   Books Book3= {title:"Obj C programming".dup, book_id : 1001};
   printBook( Book3 ); 
}
  
void printBook( Books book ) { 
   writeln( "Book title : ", book.title); 
   writeln( "Book author : ", book.author); 
   writeln( "Book subject : ", book.subject); 
   writeln( "Book book_id : ", book.book_id); 
}

編譯并執(zhí)行上述代碼后，將產(chǎn)生以下輸出-

Book title : D Programming 
Book author : Raj 
Book subject : D Programming Tutorial 
Book book_id : 6495407 
Book title : D Programming 
Book author : Raj 
Book subject : D Programming Tutorial 
Book book_id : 6495407 
Book title : Obj C programming 
Book author : Raj 
Book subject : Empty 
Book book_id : 1001

靜態(tài)成員

靜態(tài)變量僅初始化一次，如要獲得書籍的唯一ID，我們可以將book_id設(shè)為static靜態(tài)類型 ，并增加書籍ID，一個如下所示。

import std.stdio;  

struct Books { 
   char [] title; 
   char [] subject="Empty".dup; 
   int   book_id; 
   char [] author="Raj".dup; 
   static int id=1000; 
}; 
 
void main( ) { 
   Books Book1=Books("D Programming".dup, "D Programming Tutorial".dup,++Books.id ); 
   printBook( Book1 );  
   
   Books Book2=Books("D Programming".dup, "D Programming Tutorial".dup,++Books.id); 
   printBook( Book2 );  
   
   Books Book3= {title:"Obj C programming".dup, book_id:++Books.id}; 
   printBook( Book3 ); 
}
  
void printBook( Books book ) { 
   writeln( "Book title : ", book.title); 
   writeln( "Book author : ", book.author); 
   writeln( "Book subject : ", book.subject); 
   writeln( "Book book_id : ", book.book_id); 
}

編譯并執(zhí)行上述代碼后，將產(chǎn)生以下輸出-

Book title : D Programming 
Book author : Raj 
Book subject : D Programming Tutorial 
Book book_id : 1001 
Book title : D Programming 
Book author : Raj 
Book subject : D Programming Tutorial 
Book book_id : 1002 
Book title : Obj C programming 
Book author : Raj 
Book subject : Empty 
Book book_id : 1003