Extension vs defender methods

[Brian Goetz]

As Neal said, English is malleable.  If he wants to define "extension method" method to mean extended by a non-author, that's within the bounds of credibility.  We prefer to think of it as "extended after the fact".  (Another way to think of it is that the "extension" refers to the notion of interface; an interface with behavior is an "extended interface".)  

To answer Paul's question, it is the interface that is being extended, beyond its original specification.  (Though the pedantically inclined might point out that one can add a default clause to an existing "original" method, turning it into a so-called "extension method", in a mostly binary and source compatible way.)  

The "weaver" is just an implementation trick, one that injects bytecodes into classes that inherit behavior from extended interfaces.  We don't intend this to be the real implementation, but its a darn convenient way to experiment.  

On Nov 10, 2011, at 12:55 AM, Paul Benedict wrote:

> I like this clarification but we better ask the experts who built the
> weaver :-) Are the concrete classes that extend List being woven or is the
> interface?
> 
> Paul
> 
> On Wed, Nov 9, 2011 at 3:59 PM, Patrick Wright <pdoubleya at gmail.com> wrote:
> 
>> It seems clear to me - a class implementing an interface, say
>> ArrayList, is automatically *extended* (via redirection to the default
>> implementation) to support new method(s) on List which were not part
>> of List's original API. Without a default method provided by the
>> mechanism, the class would have to be modified manually. It seems like
>> a useful distinction: the class's implementation is being *extended*
>> to include implementations it does not provide itself.
>> 
>> The type in question is ArrayList - that is the type that is being
>> extended - so we are adding functionality to the class not provided by
>> its author.
>> 
>> My interpretation, anyway.
>> 
>> 
>> Best,
>> Patrick
>> 
>> 
>>> The meaning of extension in the phrase extension methods is that they
>> allow
>>> functionality to be added (i.e. extend) to a type that was not provided
>> by
>>> the author of the type.  I don't know in what sense you're using the term
>> 
>> 
>