Question

What is a good way to call a member function of template type? Will the below foo() code only compile for types that have the bla() function defined?

class A { void bla(); };

template<typename T>
void foo() {
    T t;
    t.bla();
}

int main() {
    foo<A>();
    return 0;
}

Can I use boost::enable_if to only define this function for types that have a bla() method? If yes, is that even a good idea? I imagine the idea of "concepts" (which I know nothing about) is possibly what needs to be used here.

Answer 1

For every type you try to invoke the foo function with, the compiler will generate a new foo function with the given it and compile, if you can compile the foo function with a given type, it will works.

So in your case, the foo function will work with every type that have a bla function and that have a default constructor.

Answer 2

Your code sample looks correct; it will error if instantiated on a type which does not have a bla() member, of course.

Answer 3

It will also only compile for types which are default-constructible. The compiler will throw an error for any type which is not default constructible and does not have a bla() function that can accept no arguments.

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