Usually, you do not have to, this->
is implied.
Sometimes, there is a name ambiguity, where it can be used to disambiguate class members and local variables. However, here is a completely different case where this->
is explicitly required.
Consider the following code:
template<class T>
struct A {
int i;
};
template<class T>
struct B : A<T> {
int foo() {
return this->i;
}
};
int main() {
B<int> b;
b.foo();
}
If you omit this->
, the compiler does not know how to treat i
, since it may or may not exist in all instantiations of A
. In order to tell it that i
is indeed a member of A<T>
, for any T
, the this->
prefix is required.
Note: it is possible to still omit this->
prefix by using:
template<class T>
struct B : A<T> {
using A<T>::i; // explicitly refer to a variable in the base class
int foo() {
return i; // i is now known to exist
}
};