When should I explicitly write this->member in a method of
a class?
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 {
T i;
};
template<class T>
struct B : A<T> {
T foo() {
return this->i; //standard accepted by all compilers
//return i; //clang and gcc will fail
//clang 13.1.6: use of undeclared identifier 'i'
//gcc 11.3.0: 'i' was not declared in this scope
//Microsoft C++ Compiler 2019 will accept it
}
};
int main() {
B<int> b;
b.foo();
}
If you omit this->, some compilers do not know how to treat i. 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> {
int foo() {
return A<T>::i; // explicitly refer to a variable in the base class
//where 'i' is now known to exist
}
};