对象的赋值操作符

Assignment Operator for an object

本文关键字：赋值操作符 对象      更新时间：2023-10-16

我写了一个代码，用于动态分配一个名称。我知道在这种情况下我应该处理深度拷贝。我所写的是我自己版本的复制构造函数、复制赋值操作符和析构函数。我应该重新定义任何其他隐式函数，如移动赋值操作符吗?我不清楚移动赋值操作符或任何其他隐式定义的成员函数的概念(除了我已经提到的)。谁能添加这个dynName code的代码，以显示Move赋值运算符或任何其他隐式成员函数(如果有的话)

#include <iostream>
using namespace std;
class dynName{
    char* name;
    int size;
    public:
    dynName(char* name="")
    {
        int n=strlen(name)+1;
        this->name= new char[n];
        strncpy(this->name,name,n);
        size=n;
        name[size-1]='';//NULL terminated
        cout << "Object created (Constructor) with name : "
        << name << " at address " << &(this->name) << endl;
        }
    dynName(const dynName& Ob)//Copy Constructor
    {
        int n=Ob.size;
        this->name= new char[n];
        strncpy(this->name,Ob.name,n);
        size=n;
        cout << "Object created(Copy constructor) with name : "
        << this->name  << " at address " << &(this->name) << endl;
        }
    //Assignment Operator
    dynName& operator=(const dynName& ob);
    ~dynName()
    {
        cout << "Object with name " << this->name << " at address " <<
        &(this->name)<<" destroyed" << endl;
        delete[] name;
        name=0; //Avoiding Dangling pointer if any
        }
    //friend ostream& operator << (ostream& os,const dynName ob);
    //Will Call Copy Constructor
    friend ostream& operator << (ostream& os,const dynName& ob);
    };
dynName& dynName::operator=(const dynName& ob)
{
    // check for self-assignment
        if (this == &ob)
        cout << "Created with assignment Operator " << endl;
            return *this;
        // first we need to deallocate any value that this string is holding!
        delete[] this->name;

        this->size = ob.size;
           // this->name = new char[this->size];
            strncpy(this->name, ob.name,this->size);
            cout << "Created with assignment Operator " << endl;
    return *this;
    }
//ostream& operator << (ostream& os,const dynName ob)
ostream& operator << (ostream& os,const dynName& ob)
{
    os << "The name ("<< ob.size << " Letters) : " << ob.name << endl;
    return os;
    }
int main()
{
    dynName Ob1("Andrew Thomas");
    dynName Ob2;
    dynName Ob3(Ob1);
    dynName Ob4;
    Ob4=Ob1;//Should Call Assignment Operator
    cout << "nnn";
    cout << Ob1;
    cout << Ob2;
    cout << Ob3;
    cout << Ob4;
    cout << "nnn";
    return 0;
    }
这段代码的问题是没有调用我的复制赋值操作符。有帮助吗，为什么?

。美元/试验

Object created (Constructor) with name : Andrew Thomas at address 0x22ac40
Object created (Constructor) with name :  at address 0x22ac30
Object created(Copy constructor) with name : Andrew Thomas at address 0x22ac20
Object created (Constructor) with name :  at address 0x22ac10

The name (14 Letters) : Andrew Thomas
The name (1 Letters) :
The name (14 Letters) : Andrew Thomas
The name (1 Letters) :

Object with name  at address 0x22ac10 destroyed
Object with name Andrew Thomas at address 0x22ac20 destroyed
Object with name  at address 0x22ac30 destroyed
Object with name Andrew Thomas at address 0x22ac40 destroyed

感谢

编辑

引用Move赋值操作符和' if (this != &rhs) 'Class&&是什么?我的意思是我从来没用过这种东西。只是引用，比如Class&

似乎你在这里缺少大括号:

   if (this == &ob)
    cout << "Created with assignment Operator " << endl;
        return *this;

只有输出是if主体的一部分，return语句将始终执行。

应该调用复制操作符，但总是在自赋值检查之后返回。

dynName& dynName::operator=(const dynName& ob)
{
    // check for self-assignment
        if (this == &ob)
        cout << "Created with assignment Operator " << endl;
            return *this;  //THIS LINE is not in the if block
        // first we need to deallocate any value that this string is holding!
        delete[] this->name;

        this->size = ob.size;
           // this->name = new char[this->size];
            strncpy(this->name, ob.name,this->size);
            cout << "Created with assignment Operator " << endl;
    return *this;
    }
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