Is it possible to cast an anonymous procedure to a procedure of object ?

[dormky 2]

In Data.DB, the dataset events are defined as

TDataSetNotifyEvent = procedure(DataSet: TDataSet) of object;

This means that such code as

MyTableTest.BeforeDelete := procedure (d: TDataSet) begin LogTableOperation('MyTableTestBeforeDelete'); end;

not valid. Is there anyway of casting this ? I'd rather not define a procedure in my data module for every event of every table...

[David Heffernan 2357]

24 minutes ago, dormky said:

Is there anyway of casting this ?

No, they are fundamentally different things in terms of implementation. 

[Remy Lebeau 1459]

This is documented behavior:

https://docwiki.embarcadero.com/RADStudio/en/Anonymous_Methods_in_Delphi

Quote

you cannot assign an anonymous method to a regular method pointer. Method references are managed types, but method pointers are unmanaged types. Thus, for type-safety reasons, assigning method references to method pointers is not supported. For instance, events are method pointer-valued properties, so you cannot use an anonymous method for an event.

 

[JonRobertson 76]

On 1/20/2025 at 8:19 AM, dormky said:

I'd rather not define a procedure in my data module for every event of every table...

If several tables will use events with identical functionality, such as logging, you can have a single event assigned to multiple tables:

 

procedure TForm1.AllTablesBeforeDelete(DataSet: TDataSet);
begin
  LogTableOperation(DataSet.Name + 'BeforeDelete');
end;

  MyTable1Test.BeforeDelete := AllTablesBeforeDelete;
  MyTable2Test.BeforeDelete := AllTablesBeforeDelete;
  MyTable3Test.BeforeDelete := AllTablesBeforeDelete;

Or assign the event handler to each table using the object inspector.