The following code is giving compilation error:
template <typename T>
class Base
{
public:
void bar(){};
};
template <typename T>
class Derived : public Base<T>
{
public:
void foo() { bar(); } //Error
};
int main()
{
Derived *b = new Derived;
b->foo();
}
ERROR
Line 12: error: there are no arguments to 'bar' that depend on a template parameter, so a declaration of 'bar' must be available
Why is this error coming?
The name foo()
does not depend on any of Derived
's template parameters - it's a non-dependent name. The base class where foo()
is found, on the other hand - Base<T>
- does depend on one of Derived
's template parameters (namely, T
), so it's a dependent base class . C++ does not look in dependent base classes when looking up non-dependent names.
To resolve this, you need to qualify the call to bar()
in Derived::foo()
as either this->bar()
or Base<T>::bar()
.
This C++ FAQ item explains it nicely: see http://www.parashift.com/c++-faq-lite/templates.html#faq-35.19
The code you've provided doesn't have a build error on the line you indicate. It DOES have one here:
Derived *b = new Derived;
which should read:
Derived<int> *b = new Derived<int>();
(or use whatever type you want instead of int.)
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