用于数组的delete p324

delete 对象地址;

delete 首先调用待清除对象的析构函数，然后释放内存

如果delete一个void指针，唯一发生的事情就是释放了内存。因为通过void指针，无法知道对象的类型，就无法调用其析构函数。

delete []books;

[]告诉编译器，books实际上是一个对象数组的起始地址。该代码的任务是，把数组创建时存放在某处的数组元素个数取回，并为数组的所有对象调用析构函数。

1 测试程序deleteTest.cpp

 1 #include <iostream>
 2 #include <string>
 3 
 4 using namespace std;
 5 
 6 class Book
 7 {
 8     string name;
 9     string author;
10     double price;
11 
12 public:
13     Book() : name("null"), author("null"), price(0) 
14     {
15         cout << "invoke constructor Book() " << endl;
16     }
17     Book(string name, string author, double price) : name(name), author(author), price(price) 
18     {
19         cout << "invoke constructor Book(string " << name << ", string " << author << ", double "<< price << ") " << endl;
20     }
21 
22     //复制构造函数
23     Book(const Book& b) : name(b.name), author(b.author), price(b.price) 
24     {
25         cout << "Book::Book(const Book& b)" << endl;
26     }
27 
28     ~Book()
29     {
30         cout << "~Book()" << endl;
31         cout << "free book: '" << name << "'" << endl;
32     }
33 
34     friend ostream& operator<<(ostream& os, const Book& b)
35     {
36         return os << "BookName: " << b.name << ", BookAuthor: " << b.author 
37             << ", BookPrice: " << b.price;
38     }
39 
40     //重载赋值运算符
41     Book& operator=(const Book& b)
42     {
43         cout << "Book::operator=(const Book&)" << endl;
44         name = b.name;
45         author = b.author;
46         price = b.price;
47 
48         return *this;
49     }
50 };
51 
52 
53 
54 int main()
55 {
56     //数组book里放的是Book类型的指针 -- 使用new在堆上创建对象数组
57     //在堆上为‘5个Book对象’分配了内存，并为这5个Book对象调用了构造函数
58     Book* books = new Book[5];
59     
60     Book* b1 = new Book("算法精解", "Kyle Loudon", 56.2);
61     Book* b2 = new Book("Qt程序设计", "Pulat", 10.2);
62 
63     books[0] = *b1; //
64     books[1] = *b2;
65     
66     cout << "---- delete b1 ----" << endl;
67     delete b1;
68     cout << "---- delete b2 ----" << endl;
69     delete b2;
70     
71     cout << "---- delete []books ----" << endl;
72     delete []books;
73 
74     return 0;
75 };

运行结果：

2 对象数组

Book* books = new Book[5];

使用new在堆上创建了一个包含5个Book对象的数组，books是该数组的起始地址（首地址、第一个元素的地址）

books是一个指向Book对象的指针变量，与Book* bk1 = new Book;创建一个Book对象的语法形式是一样的；但Book* books = new Book[5];编译器会记住books指向的Book对象后面还跟4个Book对象。