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taurusrow

Ternary Operator and Polymorphism

3 posts in this topic

Simplified question : Can I use the ternary operator in a new object declaration.
 
For example, if I have a two player game, and depending on whose turn it is:

 

classA { ... }

classB : classA {...}

classC : classA {...}

 

classA _Object = ((_turn % 2 == 0) ? new classB : new classC);

 

When I do this, I'm told that the operands are incompatible.  I could have sworn that I've seen this working before, but I can't seem to get it to work.  I tried restructuring and had the same results with this:

 

 

classA { ... }

classB : classA {...}

classC : classA {...}

 

classB cb;

classC cc;

 

classA _Object = ((_turn % 2 == 0) ? cb : cc);

 

Any insight would be appreciated.  Thanks!

 
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In the first case it looks like you're trying to assign a pointer to a class to a non-pointer variable type.

 

In the second case your operands are definitely different types (and anyway, you're assigning to a variable of the type of the parent class, which will cause slicing)

 

(Is this your actual code?)

 

 

 

If you're trying to assign to a pointer to classA, like the following:

 

classA *_Object = ((_turn % 2) == 0) ? new classB : new classC);

 

Then you can get it to work by static_cast'ing each of the operands to A*.

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Thanks for your replies.

 

@Phil - it wasn't my actual code, I simplified, but it was the basic idea that I couldn't get to work.  The second attempt was based on something I read in another forum and didn't think would work as it was (turns out I was right).

 

@Alvaro - thanks for the sample code.  At first I wasn't getting it to work, then realized that I wasn't static casting to a pointer of the base class.

 

Sometimes one needs to really stop looking at code, then come back with a fresh mind.  Appreciate the help!  Thanks.

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