C/C++ 语言系列（七）复合数据类型之结构体

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声明语法

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struct type_name {
  member_type1 member_name1;
  member_type2 member_name2;
  member_type3 member_name3;
  .
  .
} object_names;

定义用法

结构体对象

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// declare three objects (variables) of this type (product): apple, banana, and melon.
struct product {
  int weight;
  double price;
} apple, banana, melon;

// struct requires either a type_name or at least one name in object_names, but not necessarily both.
struct {
  int weight;
  double price;
} apple, banana, melon;

// declare three objects (variables) of this type (product): apple, banana, and melon.
product apple, banana, melon;

结构体数组

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// because structures are types, they can also be used as the type of arrays.
product banana[3];

结构体指针

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product * p = &apple;

创建结构体指针之后，可以使用以下运算符访问其成员变量：

Operator Expression What is evaluated Equivalent
dot operator (.) a.b Member b of object a
arrow operator (->)
(dereference operator)		 a->b Member b of object pointed to by a (*a).b

例子：

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apple.weight;  // 3
// The arrow operator (->) is a dereference operator that is used exclusively with pointers to objects that have members. This operator serves to access the member of an object directly from its address.
p->weight;     // 3
// equivalent to:
(*p).weight;   // 3

例子 2：

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#include <iostream>
using namespace std;

struct product {
  int weight;
  double price;
};

void test() {
  product apple;
  apple.weight = 3;
  apple.price = 4;
  product * p_apple = &apple;

  cout << "weight: " << (*p_apple).weight << endl;                // weight: 3
  cout << "weight: " << p_apple->weight << endl;                  // weight: 3

  cout << "address of apple: " << p_apple << endl;                // address of apple: 0x7ffee256b5b0
  cout << "address of weight: " << &p_apple->weight << endl;      // address of weight: 0x7ffee256b5b0
  cout << "address of price: " << &p_apple->price << endl;        // address of price: 0x7ffee256b5b8
  cout << "size of weight: " << sizeof(p_apple->weight) << endl;  // size of weight: 4
  cout << "size of price: " << sizeof(p_apple->price) << endl;    // size of price: 8
}

int main() {
  test();
  return 0;
}

结构体作为函数参数

支持三种方式的传参：

  • 传值
  • 传引用
  • 传址
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#include <iostream>
using namespace std;

struct product {
  int weight;
  double price;
} lemon;

// 传值
void show(product prd) {
  cout << "weight: " << prd.weight << " price: " << prd.price << endl;
}

// 传引用
void show2(product &prd) {
  cout << "weight: " << prd.weight << " price: " << prd.price << endl;
}

// 传址
void show3(product * prd) {
  cout << "weight: " << prd->weight << " price: " << prd->price << endl;
}

void test() {
  lemon.weight = 1;
  lemon.price = 2;
  show(lemon);    // weight: 1 price: 2
  show2(lemon);   // weight: 1 price: 2
  show3(&lemon);  // weight: 1 price: 2
}

int main() {
  test();
  return 0;
}

参考

http://www.cplusplus.com/doc/tutorial/structures/