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(0) 
    {
        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[5];
    
    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[0] = *b1; //
    books[1] = *b2;
    
    cout << "---- delete b1 ----" << endl;
    delete b1;
    cout << "---- delete b2 ----" << endl;
    delete b2;
    
    cout << "---- delete []books ----" << endl;
    delete []books;

    return 0;
};

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。