Making "super" work outside a literal?

Axel Rauschmayer axel at rauschma.de
Sat Jun 25 14:05:32 PDT 2011


>> I don’t know if this has been discussed, but I find the |super| work-around provided by YUI and CoffeeScript (in the generated code) not that bad:
>> 
>>       ThisClass.__super__.foo.call(this, arg1, arg2);
> 
> I'm not sure what you mean. If we add 'super', surely we want more than the __super__ hack. We also want a callable expression 'super' in constructors, and a 'super.foo' form for method and other property accesses from subclass methods. We don't want people writing out .call by hand.

Agreed. As a hack, it already accomplishes a lot of what |super| is supposed to, mainly not hardcoding the name of the super-class.

>> With ThisClass.__super__ pointing to SuperClass.prototype.
> 
> The CoffeeScript compiler can lexically bind ThisClass and wire up __super__ with generated runtime helper code. That's all backstage of the CoffeeScript *language*, though.
> 
> 
>> As a completely static solution, one could maybe expand a super-call
>>       super.bar(x, y);
>> to
>>       __CurrentObject__.[[Prototype]].bar.call(this, x, y);
>> 
>> On the other hand, I don’t know if a reference to __CurrentObject__ is ever available for some kind of static expansion.
> 
> Are you talking about |here| again, with a new name?

Sorry for the confusion. ;-)

I think there is a subtle difference between the two (at least as I use them):

- |here|: dynamic, computed as part of the property lookup, closely related to |this|.

- __CurrentObject__ (or possibly a better name): Static, only available inside an object literal.

> There is no static counterpart other than the one Allen proposed, the object literal directly containing the method that uses 'super'.

That would be enough. I guess I’m suggesting then to implement “super” like CoffeeScript does. Wouldn’t that be simpler?

-- 
Dr. Axel Rauschmayer

axel at rauschma.de
twitter.com/rauschma

home: rauschma.de
blog: 2ality.com





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