C/C++ 数组允许定义可存储相同类型数据项的变量，但是结构是 C++ 中另一种用户自定义的可用的数据类型，它允许您存储不同类型的数据项。
结构用于表示一条记录，假设您想要跟踪图书馆中书本的动态，您可能需要跟踪每本书的下列属性：
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Title
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Author
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Subject
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Book ID
为了定义结构，您必须使用 struct 语句。struct 语句定义了一个包含多个成员的新的数据类型，struct 语句的格式如下：
| struct [structure tag]
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| {
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| member definition;
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| member definition;
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| ...
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| member definition;
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| } [one or more structure variables]; |
structure tag 是可选的，每个 member definition 是标准的变量定义，比如 int i; 或者 float f; 或者其他有效的变量定义。在结构定义的末尾，最后一个分号之前，您可以指定一个或多个结构变量，这是可选的。下面是声明 Book 结构的方式：
| struct Books
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| {
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| char title[50];
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| char author[50];
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| char subject[100];
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| int book_id;
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| }book; |
为了访问结构的成员，我们使用成员访问运算符（.）。成员访问运算符是结构变量名称和我们要访问的结构成员之间的一个句号。您可以使用 struct 关键字来定义结构类型的变量。下面的实例演示了结构的用法：
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| #include <iostream>
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| #include <cstring>
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|
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| using namespace std;
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|
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| struct Books
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| {
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| char title[50];
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| char author[50];
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| char subject[100];
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| int book_id;
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| };
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|
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| int main( )
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| {
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| struct Books Book1;
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| struct Books Book2;
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|
|
|
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| strcpy( Book1.title, "Learn C++ Programming");
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| strcpy( Book1.author, "Chand Miyan");
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| strcpy( Book1.subject, "C++ Programming");
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| Book1.book_id = 6495407;
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|
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|
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| strcpy( Book2.title, "Telecom Billing");
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| strcpy( Book2.author, "Yakit Singha");
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| strcpy( Book2.subject, "Telecom");
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| Book2.book_id = 6495700;
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|
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| cout << "Book 1 title : " << Book1.title <<endl;
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| cout << "Book 1 author : " << Book1.author <<endl;
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| cout << "Book 1 subject : " << Book1.subject <<endl;
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| cout << "Book 1 id : " << Book1.book_id <<endl;
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|
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| cout << "Book 2 title : " << Book2.title <<endl;
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| cout << "Book 2 author : " << Book2.author <<endl;
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| cout << "Book 2 subject : " << Book2.subject <<endl;
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| cout << "Book 2 id : " << Book2.book_id <<endl;
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|
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| return 0;
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| } |
当上面的代码被编译和执行时，它会产生下列结果：
| Book 1 title : Learn C++ Programming
|
| Book 1 author : Chand Miyan
|
| Book 1 subject : C++ Programming
|
| Book 1 id : 6495407
|
| Book 2 title : Telecom Billing
|
| Book 2 author : Yakit Singha
|
| Book 2 subject : Telecom
|
| Book 2 id : 6495700 |
您可以把结构作为函数参数，传参方式与其他类型的变量或指针类似。您可以使用上面实例中的方式来访问结构变量：
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| #include <iostream>
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| #include <cstring>
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|
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| using namespace std;
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| void printBook( struct Books book );
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|
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| struct Books
|
| {
|
| char title[50];
|
| char author[50];
|
| char subject[100];
|
| int book_id;
|
| };
|
|
|
| int main( )
|
| {
|
| struct Books Book1;
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| struct Books Book2;
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|
|
|
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| strcpy( Book1.title, "Learn C++ Programming");
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| strcpy( Book1.author, "Chand Miyan");
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| strcpy( Book1.subject, "C++ Programming");
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| Book1.book_id = 6495407;
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|
|
|
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| strcpy( Book2.title, "Telecom Billing");
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| strcpy( Book2.author, "Yakit Singha");
|
| strcpy( Book2.subject, "Telecom");
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| Book2.book_id = 6495700;
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|
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| printBook( Book1 );
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|
|
|
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| printBook( Book2 );
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|
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| return 0;
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| }
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| void printBook( struct Books book )
|
| {
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| cout << "Book title : " << book.title <<endl;
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| cout << "Book author : " << book.author <<endl;
|
| cout << "Book subject : " << book.subject <<endl;
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| cout << "Book id : " << book.book_id <<endl;
|
| } |
当上面的代码被编译和执行时，它会产生下列结果：
| Book title : Learn C++ Programming
|
| Book author : Chand Miyan
|
| Book subject : C++ Programming
|
| Book id : 6495407
|
| Book title : Telecom Billing
|
| Book author : Yakit Singha
|
| Book subject : Telecom
|
| Book id : 6495700 |
您可以定义指向结构的指针，方式与定义指向其他类型变量的指针相似，如下所示：
| struct Books *struct_pointer; |
现在，您可以在上述定义的指针变量中存储结构变量的地址。为了查找结构变量的地址，请把 & 运算符放在结构名称的前面，如下所示：
为了使用指向该结构的指针访问结构的成员，您必须使用 -> 运算符，如下所示：
让我们使用结构指针来重写上面的实例，这将有助于您理解结构指针的概念：
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| #include <iostream>
|
| #include <cstring>
|
|
|
| using namespace std;
|
| void printBook( struct Books *book );
|
|
|
| struct Books
|
| {
|
| char title[50];
|
| char author[50];
|
| char subject[100];
|
| int book_id;
|
| };
|
|
|
| int main( )
|
| {
|
| struct Books Book1;
|
| struct Books Book2;
|
|
|
|
|
| strcpy( Book1.title, "Learn C++ Programming");
|
| strcpy( Book1.author, "Chand Miyan");
|
| strcpy( Book1.subject, "C++ Programming");
|
| Book1.book_id = 6495407;
|
|
|
|
|
| strcpy( Book2.title, "Telecom Billing");
|
| strcpy( Book2.author, "Yakit Singha");
|
| strcpy( Book2.subject, "Telecom");
|
| Book2.book_id = 6495700;
|
|
|
|
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| printBook( &Book1 );
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|
|
|
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| printBook( &Book2 );
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|
|
| return 0;
|
| }
|
|
|
| void printBook( struct Books *book )
|
| {
|
| cout << "Book title : " << book->title <<endl;
|
| cout << "Book author : " << book->author <<endl;
|
| cout << "Book subject : " << book->subject <<endl;
|
| cout << "Book id : " << book->book_id <<endl;
|
| } |
当上面的代码被编译和执行时，它会产生下列结果：
| Book title : Learn C++ Programming
|
| Book author : Chand Miyan
|
| Book subject : C++ Programming
|
| Book id : 6495407
|
| Book title : Telecom Billing
|
| Book author : Yakit Singha
|
| Book subject : Telecom
|
| Book id : 6495700 |
下面是一种更简单的定义结构的方式，您可以为创建的类型取一个"别名"。例如：
| typedef struct
|
| {
|
| char title[50];
|
| char author[50];
|
| char subject[100];
|
| int book_id;
|
| }Books; |
现在，您可以直接使用
Books 来定义
Books 类型的变量，而不需要使用 struct 关键字。下面是实例：
您可以使用
typedef 关键字来定义非结构类型，如下所示：
| typedef long int *pint32;
|
|
|
| pint32 x, y, z; |
x, y 和 z 都是指向长整型 long int 的指针。
