I understand what this
does, but what is the difference between *this
and this
?
Yes, I have Googled and read over *this
in my text book, but I just don't get it...
this
is a pointer, and *this
is a dereferenced pointer.
If you had a function that returned this
, it would be a pointer to the current object, while a function that returned *this
would be a "clone" of the current object, allocated on the stack -- unless you have specified the return type of the method to return a reference.
A simple program that shows the difference between operating on copies and references:
#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:
1
1
2
3
You can see that when we operate on a copy of our local object, the changes don't persist (because it's a different object entirely), but operating on a reference or pointer does persist the changes.