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

 #include <iostream>
 #include <string>

 using namespace std;

 class Book
 {
     string name;
     string author;
     double price;

 public:
     Book() : name("null"), author("null"), price()
     {
         cout << "invoke constructor Book() " << endl;
     }
     Book(string name, string author, double price) : name(name), author(author), price(price)
     {
         cout << "invoke constructor Book(string " << name << ", string " << author << ", double "<< price << ") " << endl;
     }

     //复制构造函数
     Book(const Book& b) : name(b.name), author(b.author), price(b.price)
     {
         cout << "Book::Book(const Book& b)" << endl;
     }

     ~Book()
     {
         cout << "~Book()" << endl;
         cout << "free book: '" << name << "'" << endl;
     }

     friend ostream& operator<<(ostream& os, const Book& b)
     {
         return os << "BookName: " << b.name << ", BookAuthor: " << b.author
             << ", BookPrice: " << b.price;
     }

     //重载赋值运算符
     Book& operator=(const Book& b)
     {
         cout << "Book::operator=(const Book&)" << endl;
         name = b.name;
         author = b.author;
         price = b.price;

         return *this;
     }
 };

 int main()
 {
     //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
     //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
     Book* books = new Book[];

     Book* b1 = new Book("算法精解", "Kyle Loudon", 56.2);
     Book* b2 = new Book("Qt程序设计", "Pulat", 10.2);

     books[] = *b1; //
     books[] = *b2;

     cout << "---- delete b1 ----" << endl;
     delete b1;
     cout << "---- delete b2 ----" << endl;
     delete b2;

     cout << "---- delete []books ----" << endl;
     delete []books;

     return ;
 };

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。