[fpc-devel] Re: [fpc-l] type discussion

[Marc Weustink]

listmember wrote:

>>>-- Class Contracts
>>>I like the 'require/ensure' aproach.
>>>
>>>It makes the code more robust and more debuggable, IMHO
>>
>> I think the checks you can do there are to limited. I also wonder what
>> will happen if a require isn't met. Personally I don't want
>> exeption in my released app.
>
>No, these are assertions not as exceptions.

OK, what to do if an invalid input is met ? Continue ? Skip ? Abort ?
IMO you still need some code which takes proper action

>>>-- Generics
>>>I am not sure if Generics could be done in FPC.
>>
>> There were some discussions about it here and AFAIK some are trying to
>> implement.
>
>Any links?
http://www.freepascal.org/wiki/index.php/Generics


>>>-- Virtual Properties and Events
>> The examples given there are not very different of what is
>> possible now.
>> Make SetWith virtual and you have almost the same.
>>
>> What however would be nice is if you could override the getter
>> or setter.
>> Something like
>> property Width write MySetWidth
>
>I think you missed a few things here.
>
>type
>   TMyClass = class
>     ...
>     property Width: integer read write; virtual; abstract;
>   end;
>
>As you can see, getters and setters are not in the picture
>at all. Which means, you have all the freedom you want in
>the derived class.

Which is allmost the same as a virtual abstract Getter and Setter (almost,
read/write from a field isn't covered)

>Plus, I like the idea that I could have a base class
>with read-only property that can not be overriden to be
>read-write later.
>
>     property Width: integer read; virtual; abstract;

That makes some sense (but it would be incompatible with existing code)

>OK, while I like the idea, I can not think of how I would
>use it though :-) Can someone help me out here <G>

:-)

>>>-- Enhanced Multicast Events
>
>> This is not really new. You can implement it yourself like
>>
>> property OnChange: TNotifyList;
>>
>> and then OnChange.Add(Notifyproc) or OnChange.Remove(Notifyproc)
>
>OK. Nice to be able to do that. Do I have to write my
>TNotifyList every time I need it?

Not if you have generics ;)

>>>Inline variable initializers, such as:
>>
>> [snip]
>>
>>
>>>var
>>>  Integer1: Integer = 15;
>>>  Boolean1: Boolean = False;
>>>  String1: String = 'SOME TEXT';
>>
>> Hmm.. sometimes usefull. You can put it as first lines
> > in your constructor/codeblock, but keep it thogheter in
> > say large classes can be handy.
>
>Yes, and it improved the readability, IMHO. Plus, there is
>no reason for you to alter that in constructor/codeblock too.

Not too. It is still edited at one place.

Marc