How keep constructor from being called till "ready"?

I know that if you do:

Code:

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TestClass c;
TestClass c = NULL;

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In both cases, TestClass' empty constructor is called. But I want to declare that a class has that variable but not call the constructor until the owning class' constructor is called.

Example:

Code:

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class Owner
{
protected:
    //Want this but not initialized!
    TestClass t;

public:
    Owner()
    {
          t = TestClass();
    }

    Owner(string name)
    {
          t = TestClass( name );
    }
};

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How would I do this (i.e. keep "t" from being initialized)?

In order to do this (and I'm not sure why you would), you would have to hold that variable as a pointer, and then allocate an object with "new" at the proper moment. Now that you'd used new, you need to use delete at some point, or use a smart pointer. Why are you trying to do this?

Quote:

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Originally Posted by brewbuck

In order to do this (and I'm not sure why you would), you would have to hold that variable as a pointer, and then allocate an object with "new" at the proper moment. Now that you'd used new, you need to use delete at some point, or use a smart pointer. Why are you trying to do this?

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OK, I really wanted to do it without a pointer. Is there no other way?

The reason I'm doing it is that this class is an interface into data stored in TLS and if it's constructed with an argument, it saves that to TLS otherwise it fchecks if the data is in the TLS and if not it creates the data from a configuration and stores that.

Quote:

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Originally Posted by 6tr6tr

OK, I really wanted to do it without a pointer. Is there no other way?

The reason I'm doing it is that this class is an interface into data stored in TLS and if it's constructed with an argument, it saves that to TLS otherwise it fchecks if the data is in the TLS and if not it creates the data from a configuration and stores that.

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Perhaps a class is not really the right solution here. Perhaps just create a global SetOwner() function which does this "stuff" depending on whether it was passed an argument or not. A class really, really wants to construct all of its members, so doing goofy stuff to try to avoid that behavior is probably a sign that a class is not the right design.

Surely there is an better and easier way to do this. Why not simply remove the ctr for TestClass from the default ctor for Owner? Wouldn't that accomplish the same. Thats about all I got for trying to avoid pointer usage... Why not use pointers though? It makes your unusual need more plausable

Use a pointer. Don't be scared. This is what pointers are made for.

Quote:

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But I want to declare that a class has that variable but not call the constructor until the owning class' constructor is called.

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I do not see the problem in the first place. Until the Owner constructor is invoked, the TestClass constructor for the member variable t will not be invoked since that member object cannot exist without the Owner object.

In other words, to keep t from being initialised, keep its Owner object from being initialised.

If you can, you can cut out the initialization code from the constructor and put it into a member function called Init or something. Do whatever you need to do and then call Init.
It's the easiest solution if you can do it.