Delegates: Difference between revisions

=={{header|Elena}}==

<lang elena>#import system.

#import system'routines.

#class Operable

{

#method cast:verb &to:target

= target::verb eval &delegate:$self.

#method operate

= "delegate implementation".

}

#class Delegator

{

#field theDelegate.

#constructor new

[

theDelegate := nil.

]

#method set &Delegate:obj

[

($nil == obj)

? [ theDelegate := nil. ]

! [ theDelegate := obj. ].

]

#method operate

= theDelegate cast:%eval &to:

{

delegate : o = o operate.

! : o = "default implementation".

}.

}

#symbol program =

[

#var delegator := Delegator new.

($nil, Object new, Operable new) run &each: o

[

delegator set &Delegate:o.

console writeLine:(delegator operate).

].

].</lang>