Ref to function used as interface?

[wuwuxin 28]

  {$M+}
  ReadOnlyObservable<T> = reference to function: T;
  Observable<T> = interface(ReadOnlyObservable<T>)
  {$REGION 'Property Accessors'}
    procedure Invoke(const value: T); overload;
  {$ENDREGION}
    procedure Subscribe(const action: TAction<T>; trigger: TNotifyTrigger = AfterChange);
  end;

The above is taken from @Stefan Glienke's Knockoff project
https://bitbucket.org/sglienke/knockoff/src/master/Knockoff.Observable.pas

 

Can someone give me some heads up - is this some type of advanced usage of Delphi?   can "reference to functio: T" be used as the base interface?

[DPStano 15]

https://stackoverflow.com/questions/39955052/how-are-anonymous-methods-implemented-under-the-hood

https://sergworks.wordpress.com/2010/01/27/anonimous-methods-in-delphi-the-internals/

Edited November 23, 2021 by DPStano