[fpc-pascal] TFPObjectlist example

[Sven Barth]

James Richters via fpc-pascal <fpc-pascal at lists.freepascal.org> schrieb am
Di., 8. Sep. 2020, 20:07:

> What’s the difference between TList and TFPGList?  Which one is better
> for this example?
>
The main difference is that TFPGList ist a generic, thus when you
specialize it with your record you'll have a typesafe object where you
don't need to manually work with pointers while for TList you either need
to work with pointers or declare a descendant with typesafe setters/getters
like you had done in the other mail.
You could also take a look at the generic TList in Generics.Collections
which does not require an = operator like TFPGList does.

Please note that if you work with TFPGList or the Generics.Collection.TList
then you need to modify an entry using a local variable if your entries are
records:

entry := mylist[i];
entry.field := entry.field * 2;
mylist[i] := entry;

This is because the getter for the Items property will provide a /copy/ of
the entry.

With Classes.TList you'd use a pointer however and thus you can modify it
in place.

Regards,
Sven

>
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