From: Roland Schwarz (roland.schwarz_at_[hidden])
Date: 2004-12-06 02:41:40
Jeff Garland wrote:
>I'm interested in seeing something like this in boost...
>Question -- will this compile in your implementation?
> square* ps4 = dynamic_new<square>("square", 10.0);
>as well as:
> shape* ps4 = dynamic_new<shape>("square", 10.0);
Well this depends on which types you have registered.
square* ps4 = dynamic_new<square>("square", 10.0);
you are assuming a different base class than shape, and to this
end you also would need to "declare"
But I admit since I only posted a small example to find out
the level of interest I did not put much effort to explain
my rationale and the possible range of usages.
It goes something along this:
To call a function of an object you need its interface.
I use an (not necessarily) abstract base class to describe
it. I use the covariant return types feature of C++ to
return pointers to derived classes from a creator function.
So the pattern of usage is:
baseclass* p = dynamic_new<baseclass>("derivedclass");
if the dynamic new cannot perform the requested operation at runtime it
return a 0 - pointer instead. If succesfull p points to the derived class.
To make it the exakt derived class, you need to cast it of course.
derivedclass* p = (derivedclass*)dynamic_new<baseclass>("derivedclass");
But this of course is not of much use, since it is easier then to call
derivedclass* p = new derivedclass;
since you already know everything that is needed to create the object.
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