I'm using Delphi 11. Is there a way to run a specific function inside a TDataModule, but only if this datamodule exists on my project ?

I need a way to check if the datamodule exists and call the function as string, because some projects will have this datamodule added, others not.

Instead of this :

myDataModule.myfunction(param);

Would be something like this imaginary code :

if TDataModule(findcomponent('myDataModule')) <> nil then
   TDataModule(findcomponent('myDataModule')).call('myfunction','param');

CodePudding user response：

A lightweight solution could be Messages (those from System.Messaging).

1. Declare a new TMessage descendant holding the parameters needed for the call
2. When the datamodule is created it Subscribes to this message type with a handler doing the actions.
3. Instead of searching for the datamodule just Send the message.

CodePudding user response：

This may or may not be applicable to your situation... But that seems like the kind of situation I would solve with a multicast event.

Your code would call Event.Execute('Param') instead of myDataModule.myfunction(param).

The part of your code responsible for "importing" and creating the datamodule would register to the event. Something like :

EventClient := TEventClient.create(
                    procedure (const AParam : ParamType)
                    begin
                      myDataModule.myfunction(AParam)
                    end);
EventClient.Observe(Event);

Now, this approach makes sense if the reasons to call your function is "event-like", but this might make less sense in other contexts.

As for library implementing multicast event, I can't recommend any as I always used a proprietary one. If you need inspiration to implement your own, you can look at TMultiCaster in unit Vcl.AppEvnts which implements more or less the same concept.