Re: [jruby-user] overloading Java methods via a module

By the way, include has a special hook, included that gets called whenever
include is used. A lot of Rails code uses this hook to change include‘s
behavior. For instance, making include behave more like extend. This may be
why Ruby’s default behavior was surprising.
​


On Thu, Jul 17, 2014 at 9:28 PM, Eric West <[email protected]> wrote:

> including a module won’t override the methods in the class it is included
> into. For example, I’ll run some code on MRI to explain this:
>
> $ ruby -v
> ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]
>
> module Cool
>   def lame
>     "Dude, that is so lame."
>   endend
> class Hipster
>   include Cool
>
>   def lame
>     "You've probably never heard of it. Because you're lame."
>   endend
>
> hipster = Hipster.new
> hipster.lame # => "You've probably never heard of it. Because you're lame."
>
> As you can see, despite including the module, it doesn’t override the
> method #lame. Now what I can do is call #super, watch:
>
> module Cool
>   def lame
>     "Dude, that is so lame."
>   endend
> class Hipster
>   include Cool
>
>   def lame
>     "You've probably never heard of it. Because you're lame."
>     super
>   endend
>
> hipster = Hipster.new
> hipster.lame # => "Dude, that is so lame."
>
> Including a module places that module into the class’s object heirarchy.
> So it’s method’s don’t override the class’s instance methods. Instead, they
> become super to those methods. One way to achieve something like the result
> you are after is to extend the instance of the class with the module. Like
> so:
>
> module Cool
>   def lame
>     "Dude, that is so lame."
>   endend
> class Hipster
>   def lame
>     "You've probably never heard of it. Because you're lame."
>   endend
>
> hipster = Hipster.new.extend(Cool)
> hipster.lame # => Dude, that is so lame.
>
> Hope that explains what you are running into. This actually has nothing to
> do with jruby and java, it is just how ruby works.
> ​
>
>
> On Thu, Jul 17, 2014 at 5:54 PM, Mike Luu <[email protected]> wrote:
>
>> I can’t seem to overload a Java class instance method via a module.
>>
>> ```
>>     require 'java'
>>     module A
>>       def getComment
>>         'via module'
>>       end
>>     end
>>
>>     Java::JavaNet::HttpCookie.send(:include, A)
>>     Java::JavaNet::HttpCookie.new('k', 'v').getComment
>> ```
>>
>> the last line returns the original java definition when I want it to
>> return my overloaded version
>>
>> What does work is opening up the class…
>>
>> ```
>>     require 'java'
>>     class Java::JavaNet::HttpCookie
>>       def getComment
>>         'via class opening'
>>       end
>>     end
>>     java.net.HttpCookie.new('k', 'v').getComment
>> ```
>>
>> note: I’m using HttpCookie as an example  :)
>>
>> Thanks,
>> Mike
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>