[fpc-devel] class abstract, class sealed implementation. please review.

[Florian Klaempfl]

Vinzent Höfler schrieb:
> Florian Klaempfl <florian at freepascal.org>:
> 
>> Marco van de Voort schrieb:
>>> In our previous episode, Florian Klaempfl said:
>>>>> This is exactly my point about sealed classes. When you design the
>>>>> product or class, you have NO way of know what will come in the
>>>>> future. So you need to stay flexible to change! Yet another OOP
>>>>> principal that "sealed" tries to prevent!
>>>> This might be true, but what's the difference with private etc.?
>>> Private is typically used in nearly every class, sealed in exceptional
>>> cases. At best.
>> I meant regarding "flexibility". Declaring a member private makes things
>> also less flexible.
> 
> The main difference is that "private" restricts visibility, 

It's not only not visible but neither accessible. And if something is
not accessible, it affects flexibility.

> whilst "sealed" restricts extensibility. The former is usually a good thing, the latter not.
> 
> 
> Vinzent.
>