[fpc-pascal] Overriding or reimplementing a property

[Mark Morgan Lloyd]

Marco van de Voort wrote:
> In our previous episode, Mark Morgan Lloyd said:
>> Given something like
>>
>> implementation
>>
>> var     DBConnectionNearby: TSQLConnection= nil;
>>
>> ..
>> case MainForm.NearbyKind of
>>    dbkFirebird: DBConnectionNearby := TIBConnection.Create(nil);
>>    dbkPostgres: DBConnectionNearby := TPQConnection.Create(nil);
>>
>> is there an elegant way of overriding the Connected property to point to 
>> code that can e.g. check that all prerequisite libraries are available 
>> before trying to activate the object?
> 
> Check the prequisite libraries yourself, and then if found, initialize the
> corresponding unit yourself:
> 
> e.g. in the case of postgres3dyn using
> 
> Function InitialisePostgres3(Const libpath : ansistring) : integer;

I'm doing that. What I'm checking is that I'm not overlooking some way 
of declaring/implementing DBConnectionNearby, which can be either a 
TIBConnection or a TPQConnection, with an extension to the Connected 
property. I suppose that in effect it would be some variant of multiple 
inheritance.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

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