Re: Can we use abstract class templating classes?

From:
Adrian Hawryluk <adrian.hawryluk-at-gmail.com@nospam.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 17 Mar 2007 01:54:34 GMT
Message-ID:
<uTHKh.122430$cE3.79320@edtnps89>
newbie wrote:

Say I have the following class:

class MyAbs {
  virtual ~MyAbs() {}
  virtual void foo() = 0;
  virtual void bar() {cout << "abs::bar"; }
}

class MyDer1: public MyAbs {
  MyDer1() {counter = 0; }
  foo() { cout << "der1::foo--" << counter++; }
  int counter;
}

class MyDer2: public MyAbs {
  MyDer1() {counter = 100; }
  foo() { cout << "der1::foo--" << counter--; }
  int counter;
}
-----------------------------------------
Can I do something like this? Thanks

template <class Toy>
class MyTemplateClass{
  Toy toy_;
  Play() { toy_.foo(); }
}


Yeah, but you don't need to. You are using generics (although a limited
form if I understand the term correctly) in conjunction with templates
when it isn't really necessary *in the scope of this case*. You could
do the same thing without subclassing MyAbs. Of course whatever
MyTemplateClass takes as a parameter, it must have a function foo that
takes no parameters.

Generics is a runtime solution, "I want to plug in any class at runtime
that has this interface so that I may interact with it using those
interfaces", as opposed to templates which is a compile time solution "I
want my programme to emit code that will interact with this set of
classes/or constants in the way I define."

Although, by specifying the interface class, it does make it easy to see
what functions are needed. But again it is not necessary *in the scope
of this case*.

Adrian
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