myObject.MyEvent := procedure (Sender : TObject); begin ... end;
There are of course some extensions that go beyond what Delphi supports 😉
You are allowed to use a named local procedure as a closure / anonymous method, with optional capture of local variables, allowing for neater layout of code, for instance:
begin ... procedure MyLocalProc(Sender : TObject); begin ... end; ... myObject.MyEvent := MyLocalProc; ... end;
The function pointers and closures are unified, you did not have to distinguish between a “procedure” and a “procedure of object“, and you don’t have to distinguish a “reference to procedure” either, ie. if you declare
type TNotifyEvent = procedure (Sender : TObject);
as long as the parameters match (and result type for a function) , the above type will accept standalone functions, object methods, interface methods, and now closures/anonymous methods (and even record methods, which are just syntax sugar for standalone function with an implicit parameter).
3 thoughts on “Closures in DWScript / OP4JS”
Even if I do not like very much anonymous methods, and do not mind writing some short methods or even classes for such purpose. If you take a look at the Delphi implementation of closures (when local variables are involved), there is a lot of “hidden” code generated. And I always like to know how the generated asm (or execution stack for a script) will look like, when I code. 🙂
Could you provide some general links about closure-based engine for runtime execution? I understand that e.g. DWS and LUA have a stack based runtime, but I don’t get the “closure” thing in term of execution runtime – or is it just a feature, not a proper design?
Can’t we get rid of the method signature we have to write every time using a closure? This can be taken from the method declaration.
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