C++创建对象时什么时候用*,什么时候不用*

用*, 表示创建的是一个指针对象，C++中用new关键字开辟内存。

另外指针对象访问成员变量用-> , 非指针用. 就这么个原则

但是指针也可以不用-> 例如 （*p）.age  所以->其实就是先*后.的简写吧

 

同样一个问题：

C++用new和不用new创建类对象区别？

使用new, 必须配套使用delete，调用delete时才会调用析构函数，若不delete，那么可能造成内存泄漏, delete时还要注意，delete NULL会崩溃
不用new, 析构函数会自动执行

代码：

 

#include <iostream>
#include <string.h>

using namespace std;

class Person{
    
public:
    ~Person(){
        cout << "Person析构函数" << endl;
    }
    
public:
    string *name;
    int age;
    
};

int main(int argc, const char * argv[]) {
    // insert code here...
    std::cout << "Hello, World!\n";
    
//    Person *p1 = new Person();
//    cout << p1->age << endl;
//    delete p1;
    
    
    Person p2 = Person();
    cout << p2.age << endl;
    
    
    
    return 0;
}

 

 

 

下面是一个简单的动态数组的代码：

 

#ifndef MyArray_hpp
#define MyArray_hpp

#include <stdio.h>

class MyArray {
    
    
public:
    MyArray();
    MyArray(int capacity);
    MyArray(const MyArray& array);
    
    ~MyArray();
    
    
    //尾插法
    void push_Back(int val);
    
    //根据索引获取值
    int getData(int index);
    
    //根据索引设置值
    void setData(int index,int val);
    
private:
    int *pAdress;
    int m_Size;
    int m_Capacity;
    
};

#endif /* MyArray_hpp */

 

#include "MyArray.hpp"
#include <iostream>
using namespace std;

MyArray::MyArray()
{
    this->m_Capacity = 100;
    this->m_Size = 0;
    this->pAdress = new int[this->m_Capacity];
}

MyArray::MyArray(int capacity){
    this->m_Capacity = capacity;
    this->m_Size = 0;
    this->pAdress = new int[this->m_Capacity];
}

MyArray::MyArray(const MyArray& array){

    this->pAdress = new int[array.m_Capacity];
    this->m_Size = array.m_Size;
    this->m_Capacity = array.m_Capacity;
}

MyArray::~MyArray(){
    
    cout << "析构函数调用" << endl;
    if (this->pAdress != NULL) {
        delete [] this->pAdress;
        this->pAdress = NULL;
    }
    
}

void MyArray::push_Back(int val){
    this->pAdress[this->m_Size] = val;
    this->m_Size++;
}

int MyArray::getData(int index){
    return this->pAdress[index];
}

void MyArray::setData(int index, int val){
    this->pAdress[index] = val;
}

 

void test01(){
    
    MyArray *array1 = new MyArray(30);
    //(MyArray *) array1 = 0x0000000100648440
    
    MyArray array2;
    /*
         {
         pAdress = 0x0000000100649240
         m_Size = 0
         m_Capacity = 100
         }
     */
    MyArray array = MyArray(30);
    /*
          {
          pAdress = 0x000000010064b680
          m_Size = 0
          m_Capacity = 30
          }
      */
}

 

这位老师说的很细 https://blog.csdn.net/qq_35644234/article/details/52702673