[fpc-pascal] property or public

[Joao Morais]

Matt Emson wrote:
> Joao Morais wrote:
>> Damien Gerard wrote:
>>>
>>> On Jan 21, 2008, at 2:52 PM, Joao Morais wrote:
>>>
>>>> Damien Gerard wrote:
>>>>> I have (it would seem) a stupid question :)
>>>>> We have TStringList vars. User can do what he want with it.
>>>>> Which one is the stupid or the better way to do it ?
>>>>> TMyClass = class(TObject)
>>>>> public
>>>>>   <snip>
>>>>>   List1: TStringList;
>>>>>   List2: TStringList;
>>>>> end;
>>>>> or
>>>>> TMyClass = class
>>>>> private
>>>>>   FList1: TStringList;
>>>>>   FList2: TStringList;
>>>>> public
>>>>>   property List1: TStringList read FList1;
>>>>>   property List2: TStringList read FList2;
>>>>> end;
>>>>
>>>> The later, *much* better. You should never use class members outside 
>>>> the private area.
>>>
>>> Thanks ! What is the reason ? I am happy I was right but I need some 
>>> reason :)
>>
>> Encapsulation, on behalf of the integrity of the instance.
>>
> 
> Implementation detail is also a good example. Then:
> 
> TMyClass = class
> private
>  FList1: array of string; //convoluted, but uses a different storage 
> mechanism
>  FList2: array of string;
> 
> protected
>  function GetList1: TStringList; virtual;
>  function GetList1: TStringList; virtual;
> 
> public
>  property List1: TStringList read GetList1;
>  property List2: TStringList read GetList2;
> end;
> 
> You can implement the storage for GetList1 and GetList 2 any way that 
> you wish internally, but give a uniform external interface.

Exact, polymorphism is also a reason. You can have abstract methods and 
no class members if the design requires. The interface continues the same.

--
Joao Morais