[fpc-pascal] flexible record design

Michael Van Canneyt michael at freepascal.org
Fri May 28 18:55:51 CEST 2010

On Fri, 28 May 2010, spir ☣ wrote:

> On Fri, 28 May 2010 16:03:28 +0200 (CEST)
> Michael Van Canneyt <michael at freepascal.org> wrote:
>> TStrings provides an abstract interface. It allows you to associate an
>> object with each string in the list.
>> This means you can do a
>>    L.Strings[i]:=Key;
>>    L.Objects[i]:=MyObject;
>> Or, in 1 statement:
>>    L.AddObject(Key,MyObject);
>> And you can retrieve it with
>>    I:=L.IndexOf(MyKey);
>>    If (I=-1) then
>>     // no mykey in list
>>    else
>>     MyObject:=L.Objects[i];
> Thank you very much, that's what I needed to understand.
> If I get it right, using the Objects property is analog to what I intended to do with a TStringList for names // to a TFPList for values.
>> However, it does not actually implement this; it just provides a common
>> API for a string list with associated objects.
>> TStringList actually implements - in a simplistic way - the functionality
>> to store the strings, and the associated objects.
> All right, now I get it. Just a point about doc: Some methods implemented in TStringList, but virtual in TString, are listed in the interface of TStringList at http://www.freepascal.org/docs-html/rtl/classes/tstringlist.html. But the ones dealings with associated objects aren't listed there (including the Objects property). This feature is also not mentionned in the description. So, I thought TStringList simply does not implement this functionality.
> Another point: in the description of TList and TFPList is written that the notification system (not implemented on TFPList) is slows down some mechanisms. Is there a version of TStringList without this feature.
> I need the simplest and most efficient version, because the type I'm now designing will be the elementary building block of a rather big system.

TStringList doesn't have the notification mechanism.


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