[cpp] view plaincopyprint?
#include <iostream>
#include <cstring>
using namespace std;
class Internet
{
public:
Internet(char *name,char *url)
{
this->name = new char[strlen(name)+1];
this->url = new char[strlen(url)+1];
if(name!=NULL)
{
strcpy(this->name,name);
}
if(url!=NULL)
{
strcpy(this->url,url);
}
}
Internet(Internet &temp)
{
this->name=new char[strlen(temp.name)+1];
this->url=new char[strlen(temp.url)+1];
if(this->name)
{
strcpy(this->name,temp.name);
}
if(this->url)
{
strcpy(this->url,temp.url);
}
}
~Internet()
{
delete[] this->name;
delete[] this->url;
}
Internet& operator =(Internet &temp)//賦值運算符重載函數
{
delete[] this->name;
delete[] this->url;
this->name = new char[strlen(temp.name)+1];
this->url = new char[strlen(temp.url)+1];
if(this->name!=NULL)
{
strcpy(this->name,temp.name);
}
if(this->url!=NULL)
{
strcpy(this->url,temp.url);
}
return *this;
}
public:
char *name;
char *url;
};
int main()
{
Internet a("王世晖的專欄","blog.csdn.net/shihui512");
Internet b = a;//b對象還不存在，所以調用拷貝構造函數，進行構造處理。
cout<<b.name<<endl<<b.url<<endl;
Internet c("清水河畔外網","bbs.qshpan.com");
b = c;//b對象已經存在，所以系統選擇賦值運算符重載函數處理。
cout<<b.name<<endl<<b.url<<endl;
}
/*****************************
運行結果：
王世晖的專欄
blog.csdn.net/shihui512
清水河畔外網
bbs.qshpan.com
******************************/
#include <iostream>
#include <cstring>
using namespace std;
class Internet
{
public:
Internet(char *name,char *url)
{
this->name = new char[strlen(name)+1];
this->url = new char[strlen(url)+1];
if(name!=NULL)
{
strcpy(this->name,name);
}
if(url!=NULL)
{
strcpy(this->url,url);
}
}
Internet(Internet &temp)
{
this->name=new char[strlen(temp.name)+1];
this->url=new char[strlen(temp.url)+1];
if(this->name)
{
strcpy(this->name,temp.name);
}
if(this->url)
{
strcpy(this->url,temp.url);
}
}
~Internet()
{
delete[] this->name;
delete[] this->url;
}
Internet& operator =(Internet &temp)//賦值運算符重載函數
{
delete[] this->name;
delete[] this->url;
this->name = new char[strlen(temp.name)+1];
this->url = new char[strlen(temp.url)+1];
if(this->name!=NULL)
{
strcpy(this->name,temp.name);
}
if(this->url!=NULL)
{
strcpy(this->url,temp.url);
}
return *this;
}
public:
char *name;
char *url;
};
int main()
{
Internet a("王世晖的專欄","blog.csdn.net/shihui512");
Internet b = a;//b對象還不存在，所以調用拷貝構造函數，進行構造處理。
cout<<b.name<<endl<<b.url<<endl;
Internet c("清水河畔外網","bbs.qshpan.com");
b = c;//b對象已經存在，所以系統選擇賦值運算符重載函數處理。
cout<<b.name<<endl<<b.url<<endl;
}
/*****************************
運行結果：
王世晖的專欄
blog.csdn.net/shihui512
清水河畔外網
bbs.qshpan.com
******************************/
the correct and safe version of the MyClass assignment operator would be this:
MyClass& MyClass::operator=(const MyClass &rhs) {
// Check for self-assignment!
if (this == &rhs) // Same object?
return *this; // Yes, so skip assignment, and just return *this.
... // Deallocate, allocate new space, copy values...
return *this;
}Or, you can simplify this a bit by doing:
MyClass& MyClass::operator=(const MyClass &rhs) {
// Only do assignment if RHS is a different object from this.
if (this != &rhs) {
... // Deallocate, allocate new space, copy values...
}
return *this;
}Remember that in the comparison, this is a pointer to the object being called, and &rhs is a pointer to the object being passed in as the argument. So, you can see that we avoid the dangers of self-assignment with this check.
In summary, the guidelines for the assignment operator are:
Take a const-reference for the argument (the right-hand side of the assignment).
Return a reference to the left-hand side, to support safe and reasonable operator chaining. (Do this by returning *this.)
Check for self-assignment, by comparing the pointers (this to &rhs).
