Object of same type as class

In c++ how do I have an object as the same type as its containing class eg:

class Test
{
public:

private:
开发者_如何学编程  Test t;
};

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Short answer, you can't.

You can have a pointer to an object of the same type, but not an object itself.

If you NEED to do this (i.e.) can't use a pointer, your design is probably wrong. If you can use a pointer, use it.

Some reasons:

You'd have to create the object on instantiation, that means an infinite recursive call on the constructor.

What would the sizeof() for the object be?

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You can't do that, since it would require infinite recursion. (Your t would contain another t, so you'd have t.t.t.t.t.t.t.t.... ad infinitum). What you could do though is put a pointer to another object inside, e.g.

private:
   Test *t;

The problem is that when you write:

Test t;

The compiler needs to know the size of Test in order to provide sufficient storage. At the point where you wrote Test t; that size isn't known because the compiler hasn't seen the end of the definition of Test (i.e. the ; after the closing }) and thus can't determine the size of it.

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That's not possible. At the max you can have a reference or pointer of the same class within it.

class Test
{
private:
  Test *t;
};

As a side note, static objects are allowed. This is because, they are not actually bound with any particular instance of class object. i.e.:

class Test
{
private:
  Test t; // error
  static Test st; // ok!
};  // define 'st' in the translation unit