CODEWITHSUNDEEP
c++
ian
ian

Reputation: 9

how to use a user defined types in other class, which is defined in some class?

just guess we have class like

class A{
public:
struct B{
...
};
typedef B C;
};

then, I'd like to use the C type in other class, that is other cpp.

how to use it?

Thanks

Upvotes: 0

Views: 74

Answers (2)

DawidPi
DawidPi

Reputation: 2365

If you declare a class, then in the class declaration you are in the namespace of the class. Let's have a look at a simple class:

class Sample{
public:
    void doSomething();
};

And let's say we also have a namespace:

namespace sampleNamespace{
    void doAnotherThing();
}

If you want let's say a pointer for both of those functions you would say:

auto* ptrFunction = Sample::doSomething;
auto* ptrAnotherFunction = sampleNamespace::doAnotherThing;

So the syntax itself is the same. Now let's take your example into account:

class Sample{
public:
   struct A{};
   typedef B A;
};

and let's convert it to the namespace conventions:

namespace Sample{
   struct A{};
   typedef B A;
}

Now if you want to use struct A you can do both (but members must be publicly visible):

//first option
Sample::A variableName;

//second option
Sample::B variableName;

Although you cannot of course use using namespace to achieve this :) So in general in cases like this you can think of classes like of namespaces.

Upvotes: 3

Xk0nSid
Xk0nSid

Reputation: 991

You can simply just include the .h i.e header file and use A::C. For e.g

Header.h

class Demo {
  public:
    struct A {
      int data;
    };
    typedef A B;
};

Main.cpp

#include <iostream>
#include "Header.h" // This is important

int main() {
  Demo::B *v = new Demo::B;
  v->data = 5;

  // This will print "The data is: 5"
  cout << "The data is: " << v->data << endl;
  delete(v);
  return 0;
}

Upvotes: 0

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