[Qt-interest] = 0 ?

[Stephen Collyer]

On 23 February 2010 12:26, Lucas Pereira Caixeta <lpcnew at gmail.com> wrote:

>
> Hi all,
>
> In my interface i have this method: virtual String getName () = 0;
>
> why this method have  "=0" in the end?
> so that it serves?
>
> This has nothing to do with Qt. It's a C++ feature. When you declare
a method with = 0, you are creating a class that can't be instantiated.
This is called a pure virtual method.

You can only use this class as as a base of another class, and you must
provide a definition of the pure virtual method to be able to instantiate
the
class.

The reason this is useful is that it allows a designer to create a class
which
specifies the interface of a class, but which doesn't provide all the
functionaltity itself.

-- 
Stephen Collyer
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