CODEWITHSUNDEEP
c++templatesmetaprogrammingenable-ifc++-concepts
Alan Turing
Alan Turing

Reputation: 12581

C++ template type which has a specific member method

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.

Upvotes: 0

Views: 175

Answers (3)

Baptiste Wicht
Baptiste Wicht

Reputation: 7663

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.

Upvotes: 2

Puppy
Puppy

Reputation: 146968

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.

Upvotes: 1

bdonlan
bdonlan

Reputation: 231283

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

Upvotes: 1

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