*this vs this in C++
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*this vs this in C++
提问by Mark Rushakoff
I understand what thisdoes, but what is the difference between *thisand this?
我明白是什么this意思，但是*this和之间有什么区别this？
Yes, I have Googled and read over *thisin my text book, but I just don't get it...
是的，我*this在我的教科书中搜索并阅读了谷歌，但我就是不明白......
回答by Mark Rushakoff
thisis a pointer, and *thisis a dereferenced pointer.
this是一个指针，并且*this是一个解除引用的指针。
If you had a function that returned this, it would be a pointer to the current object, while a function that returned *thiswould be a "clone" of the current object, allocated on the stack -- unlessyou have specified the return type of the method to return a reference.
如果您有一个返回 的函数this，它将是指向当前对象的指针，而返回的函数*this将是当前对象的“克隆”，分配在堆栈上——除非您指定了该方法的返回类型返回一个引用。
A simple program that shows the difference between operating on copies and references:
一个简单的程序，显示了操作副本和引用之间的区别：
#include <iostream>
class Foo
{
public:
Foo()
{
this->value = 0;
}
Foo get_copy()
{
return *this;
}
Foo& get_copy_as_reference()
{
return *this;
}
Foo* get_pointer()
{
return this;
}
void increment()
{
this->value++;
}
void print_value()
{
std::cout << this->value << std::endl;
}
private:
int value;
};
int main()
{
Foo foo;
foo.increment();
foo.print_value();
foo.get_copy().increment();
foo.print_value();
foo.get_copy_as_reference().increment();
foo.print_value();
foo.get_pointer()->increment();
foo.print_value();
return 0;
}
Output:
输出：
1
1
2
3
You can see that when we operate on a copyof our local object, the changes don't persist (because it's a different object entirely), but operating on a reference or pointer doespersist the changes.
您可以看到，当我们对本地对象的副本进行操作时，更改不会持久化（因为它完全是不同的对象），但对引用或指针的操作确实会持久化更改。
回答by Marcelo Cantos
thisis a pointer to the instance of the class. *thisis a referenceto the same. They are different in the same way that int* i_ptrand int& i_refare different.
this是指向类实例的指针。*this是对相同的引用。它们以相同的方式不同，int* i_ptr并且int& i_ref不同。
回答by Chris Hafey
There is no real difference, this->foo()is the same as (*this).foo().
没有真正的区别，this->foo()是一样的(*this).foo()。
