CODEWITHSUNDEEP
c++classfunction
Cemre Mengü
Cemre Mengü

Reputation: 18754

Accessing external function from a class defined in the same file

If I have a class definition

class myClass
{
  void x(); 
};


void myClass::x()
{
   hello(); // error: ‘hello’ was not declared in this scope
}

void hello()
{
   cout << "Hello\n" << endl;
}

How can I call a function defined outside the scope of a class and located in the same file ? I know that I can use Namespace::function but I am not sure in this case what I should use for Namespace

Upvotes: 0

Views: 2544

Answers (2)

pb2q
pb2q

Reputation: 59637

Define the hello function in the file ahead of where it's being used - before method x - or supply a function prototype ahead of where it's being used:

void hello();  // function definition is later in the file

void myClass::x()
{
   hello();
}

Upvotes: 4

Luchian Grigore
Luchian Grigore

Reputation: 258618

You must at least declare it (if not define it) before its use.

Usually, this is done in an anonymous namespace if the function's functionality is only used in that translation unit:

class myClass
{
  void x(); 
};

namespace
{
   void hello()
   {
      cout << "Hello\n" << endl;
   }
}

void myClass::x()
{
   hello(); // error: ‘hello’ was not declared in this scope
}

This gives the function internal linkage (similar to declaring it static) and is only available in that TU.

Upvotes: 5

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