动态数组...复制构造函数，析构函数，重载赋值运算符 [英] Dynamic array... copy constructor, destructor, overloaded assignment operator

问题描述

我正在学习中期考试。将有一个关于动态设置数组的问题，可能做一个复制构造函数，一个析构函数和重载赋值运算符。你能否证实我是否正确？另外我不明白什么是重载赋值运算符的意思。你能帮我一下吗？

I am studying for my midterm exam. There is going to be a question about setting up an array dynamically, and maybe doing a copy constructor, a destructor and overloading the assignment operator. Can you please verify if I am correct. Also I don't understand what overloading the assignment operator means. Can you help me out with this?

class A
{
int* myArray;   //basically I created a pointer called myArray, 
A()             //are my copy constructors correct? A(), and A(int size)?
{
    myArray = 0;
}
A(int size)
{
    myArray = new int[size];
}
~A()             // I think my destructor is correct
{
    delete [] myArray;
}

您能检查我的代码吗？

Can you check my code please? Also how do I overload assignment operator?

推荐答案

复制构造函数用于基于另一个相同类型的实例创建对象。你没有这样。您可以使用如下代码定义它：

The copy constructor is used for creation of object based on another's instance of the same type. You don't have such. You can define it using code like this:

A(const A &other)
{
   myArray = new int[other._size];
   _size = other._size;
   memcpy(myArray, other.myArray, sizeof(int) * _size);
}

您应该更改类，因此它将存储_size数组，需要将您的构造函数和析构函数的公开范围更改为public。

You should change your class, so it will store _size of array, you also need to change visibility of your constructors and destructor to public.

重载的赋值运算符应如下所示：

The overloaded assignment operator should look like this:

const A &operator=(const A &other)
{
   if(this == &other) return *this; // handling of self assignment, thanks for your advice, arul.
   delete[] myArray; // freeing previously used memory
   myArray = new int[other._size];
   _size = other._size;
   memcpy(myArray, other.myArray, sizeof(int) * _size);
   return *this;
}

您还可以在此赋值运算符中添加数组大小相等的检查，因此您将重用动态数组，而不必重新分配内存。

You also can add a check of equality of array sizes in this assignment operator, so you will reuse your dynamic array without unnecessary reallocations of memory.

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