tester.cpp

gistfile1.txt

#include <stdio.h>
#include "other.h"
#include "tester.h"

namespace other {
    void other_type::some_method() {
        printf("here\n");
    }
}

void Foo::foo(other::other_type* o) {
    o->some_method();
}

int main() {
    Foo f;
    other::other_type o;
    f.foo(&o);
    return 0;
}

other.h

namespace other {
  class other_type {
  public:
    void some_method();
  };
};

tester.h

namespace other {
  class other_type;
}

class Foo {
 public:
  void foo(other::other_type* o);
};