member variable of type reference of class having no default constructor

How can I use reference of a Class type which doesnt have a no argument default constructor as a member variable in another class ?
I am using references here like this.
x.h

Code:

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class X{
  public:
    X(int v);
    ~X();
  private:
    int val;
};

---

x.cpp

Code:

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#include "x.h"

X::X(int v): val(v){}
X::~X(){}

---

y.h

Code:

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#include "x.h"

class X;

class Y{
  public:
    Y();
    ~Y();
  private:
    X& xi;
};

---

y.cpp

Code:

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#include "y.h"

Y::Y():xi(2){}
Y::~Y(){}

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The above yields compilation errors

Code:

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error: invalid initialization of non-const reference of type ‘X&’ from a temporary of type ‘int’

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If I use

Code:

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Y::Y():xi(X(2)){

}

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Compiler Fires

Code:

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error: invalid initialization of non-const reference of type ‘X&’ from a temporary of type ‘X’

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However although this works but I wonder and not sure too how much logical and leagal and structured this code is (my intention is safe null reference somehow).

Code:

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Y::Y():xi(*(new X(2))){

}

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the above compiles;

Quote:

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How can I use reference of a Class type which doesnt have a no argument default constructor as a member variable in another class ?

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By storing an X reference member, there is the implication that this member is not owned by the Y object. Consequently, I would expect the Y constructor to take an X&, and then use this argument to initialise the reference member. You probably want to either implement the copy constructor in a similiar way, or disable it by declaring it as a private member. You should also probably just declare as private the copy assignment operator.

Quote:

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However although this works but I wonder and not sure too how much logical and leagal and structured this code is (my intention is safe null reference somehow).

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It's legal, but then your Y object now pretty much has ownership over the X object in question, so you should simply store an object or a (smart) pointer instead of a reference.

actually its kinda Circular Composition so the constructor just cant take the reference.
I am trying to explaining more.

Code:

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class Request: public RawRequest{
  private:
    Session& session;//Request object have a Session reference which must be initialized through initializer list
  public:
    Request(HttpHeader& headerRefObj);
    ~Request();
  .....
};

---

Code:

---

class Session{
  public:
    Session(Request& req);//Session must have a Request Object
    Session(Request& req, const string&);
    ~Session();
  private:
    Request& requestRef;
  .....
};

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so the Dilemma is Session class cant be instantiated before Request but the request Class must initialize the the Session& member variable through its constructor.

so what I am doing is:

Code:

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HttpHeader header;
Request request(header);
//Here the Request's constructor will use a way similer to *(new X(2)) show before
Session session(request);

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but the problem with it is *(new X(2)) will stay in memory untill and unless the delete is called. and as its an anonumoys variable I cant delete it from the destructor.

so there will be a big memory leack cause both Request and session require more or less huge ammount of memory and whenever the application is used a chunk of memory is wasted.

What is the relationship between Session and Request? From your code, it looks like a Request owns its Session, but the Session maintains a reference to the Request that owns it. If this is the case, then store a (smart) pointer to the Session in Request, upon which you can do something like:

Code:

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Request::Request(HttpHeader& headerRefObj)
{
    session = new Session(*this);
    // ...
}

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No both of Session and Request is owned by itself but both of these have a reference to another one. e.g. Session has a reference to request and request has the reference to session.
and there will be only one instance of session and one instance of request.

Quote:

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Originally Posted by noobcpp

No both of Session and Request is owned by itself but both of these have a reference to another one. e.g. Session has a reference to request and request has the reference to session.
and there will be only one instance of session and one instance of request.

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Why do you want each object to have a reference to the other, but yet, neither owns the other - usually there is a owner/owned relationship when you have references to other objects - that way, it's clear who creates which object, and when/where it gets destroyed.

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Mats