Method References

[Fredrik Öhrström]

Joshua Bloch wrote:
> or could we allow:
>
>     cb = #saveState;
>
>   
When you bind a callback to your own code in the constructur, then you want
to use
  my_button.onClick(this#saveState);

When you bind a callback between two objects that you have created then you
want to use:
  model.onChange(view#notify);

Sometimes you are interested in acquiring a function that encapsulates 
the virtual dispatch
of a particular message (ie method name). I call this a "stored 
message". This could be
acquired using:
  MyApp#saveState
and would be equivalent to the lamda:
  #(MyApp a) a.saveState()

You might also want to refer to the static function:
  MyApp#staticSaveState

So, should #saveState  be:
  1) this#saveState
  2) MyApp#saveState
  3) MyApp#saveState that is static
  4) Not allowed at all.

I would like the following three expressions to be identical (sed 
s/invoke//g if you like that better, I don't):

reziver.message();
(#message).invoke(reziver);
(reziver#message).invoke();

 From this follows that #saveState will give you a stored message if 
saveState uniquely identifies a method in the enclosing class. If 
#saveState uniquely identifies a static function, then it will be that 
static function.

//Fredrik

> Not only is this more succinct, but it mirrors the rules for method
> invocation, allowing "reasoning by analogy" and reducing programmer
> astonishment.
>
>             Josh
>
> On Fri, Feb 26, 2010 at 8:15 AM, Neal Gafter <neal at gafter.com> wrote:
>
>   
>> On Fri, Feb 26, 2010 at 2:45 AM, Rémi Forax <forax at univ-mlv.fr> wrote:
>>
>>     
>>> there is a source compatibility issue if you allow to not specify the
>>>       
>> type.
>>     
>>> class A {
>>>   void m(String s) { ... }
>>> }
>>> ....
>>> ref = A#m;
>>>
>>> Now suppose I want to add a new method m(Integer),
>>>
>>>       
>> Adding a new method to a class is not a source-compatible change today.
>>  However, it is a binary-compatible change today and both with and without
>> method references and with or without the proposed method reference
>> argument
>> inference.
>>
>>
>>     
>
>