Is it possible to declare an object of a class as a member variable of same class?

Question

This may sound silly, I don't know.

class Example {
 private:
       Example x; 
 public:
       //Methods
 };

It is possible in JAVA, but in C++ it is showing error. (field 'x' has incomplete type )

How can I do this in C++? If not what are other ways to do the same. I know one, pointers :) Anything else?

Also, I would be happy to know, what restricts to do the same in C++.

Thanks.

A class that contains itself. What is it's size (`sizeof(Example)`)? — Johannes Kuhn, Aug 07 '20 at 20:44
Java only supports reference semantics for user defined types... — StoryTeller - Unslander Monica, Aug 07 '20 at 20:45

score 1 · Answer 1 · edited Aug 07 '20 at 20:51

1

Ref: Self Referential Structures

This is not allowed in c++ as it will be recursive structure. However, you can use a Pointer having the address of same class type(Self Referential Pointer)

class A
{
    A* aObj; // Self Referential Pointer
}

edited Aug 07 '20 at 20:51

user4581301

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answered Aug 07 '20 at 20:46

Karthik Radhakrishnan

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Link is of questionable value. It starts off good, then wanders into graph-specific details that aren't relevant in the general case. – user4581301 Aug 07 '20 at 20:54
got the idea of recursive structure. Is it possible to do the same by any other method except pointers? – Ashutosh Rana Aug 07 '20 at 20:55
Since in the original question `Example` clearly owns `x`, then in your example `aObj` should be `std::unique_ptr aObj` instead of `A* aObj`. You'll need to implement copy assignment and copy construction explicitly. – François Andrieux Aug 07 '20 at 20:55
Worth mentioning also the possibility of `std::shared_ptr` and `std::weak_ptr` along with `std::unique_ptr` proposed by @FrançoisAndrieux. See also: https://stackoverflow.com/questions/63365537/c-instance-of-same-class/63365597#63365597 – Amir Kirsh Aug 12 '20 at 10:05

Is it possible to declare an object of a class as a member variable of same class?

1 Answers1