[Lazarus] Can I delete a property from a collectionitem

Michael Van Canneyt michael at freepascal.org
Wed Oct 12 18:21:34 CEST 2022

On Wed, 12 Oct 2022, nibbikfrans via lazarus wrote:

> Hi,
> I have a collection stored in a file. One property of each collectionitem is 
> a value of what seeems to be a set but is not. That property is no longer 
> needed. Is there a way to delete that property? 
> I suppose I can do that by 
> creating a new collectionitem type without that property and migrate the 
> data. But then a have a different collection which meens a have to make lots 
> of changes.

Yet that is the only correct way.

If you can make a descendent, you can
override the property and simply discard the value when it is set in the

> If deleting a property isn't possible, how can I delete the value of that 
> property?

In the file, in the instance of the collectionitem or where ?

> And an extra question is: how can I test whether the property has a value or 
> not?
> The possible value is defined as followes:
> TTest = (test1, test2, test3);
> TTestValues = set ot TTest;

The property has a set as value ?

If the set is empty, then the property has no value ? 
Unless empty value is also a value.


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