new delete初探
1,new有2个作用
2,delete也有2个作用
如果用new开辟一个类的对象的数组,这个类里必须有默认(没有参数的构造函数,或者有默认值的参数的构造函数)的构造函数。
释放数组时,必须加[]。delete []p
也可以用malloc,free,但是malloc不会自动调用类的构造函数,free也不会自动调用类的析构函数。
include <iostream>
#include <malloc.h>using namespace std;void c_1(){//c方式的内存空间的动态开辟 int n;cin >> n;int *p = (int*)malloc(sizeof(int) * n);for(int i = 0; i < n ; ++i){p[i] = i;}free(p);
}void cpp_1(){//c++方式的内存空间的动态开辟 int m;cin >> m;int *q = new int[m];for(int i = 0; i < m ; ++i){q[i] = i;}//释放数组的空间,要加[] delete []q;
}class Test{
public:Test(int d = 0) : data(d){cout << "create" << endl;}~Test(){cout << "free" << endl;}
private:int data;
};void c_2(){Test *t = (Test*)malloc(sizeof(Test));free(t);
}
void cpp_2(){Test *t = new Test(10);delete t;
}
int main(){c_1();cpp_1();c_2();cpp_2();Test *t = new Test[3]; delete []t; return 0;
}