include_package strangeness

[Tim Hanson]

I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:

module Util
  include_package 'java.util'

  class ArrayList
     def baz
       size
     end
  end
end

l = Util::ArrayList.new
l.add 5 # <- This fails with "undefined method `add' for #<Util::ArrayList:0x16b61c3>"

Tim

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[David Calavera]

I'm not sure if that's what you want to do, but I think you have to declare the class to extend with the fully qualified name. This works for me, from jirb:

irb(main):022:0> module Util

irb(main):023:1>  include_package 'java.util'

irb(main):024:1> 

irb(main):025:1*  class Java::JavaUtil::ArrayList

irb(main):026:2>     def baz

irb(main):027:3>       size

irb(main):028:3>     end

irb(main):029:2>  end

irb(main):030:1> end

irb(main):033:0> l = java.util.ArrayList.new     

=> #<Java::JavaUtil::ArrayList:0xe11a87 @java_object=#<Java::JavaObject:0x94cbe2>>

irb(main):034:0> l.add 5                    

=> true

irb(main):035:0> l.baz                      

=> 1

On Fri, Jul 17, 2009 at 10:05 PM, Timothy Hanson <thanson@...> wrote:

I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:

module Util
 include_package 'java.util'

 class ArrayList
    def baz
      size
    end
 end
end

l = Util::ArrayList.new
l.add 5 # <- This fails with "undefined method `add' for #<Util::ArrayList:0x16b61c3>"

Tim

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[David Calavera]

So, if you want to use your namespace you have to extend the class outside the namespace definition, or at least it's how I do it, this is an example:

http://pastie.org/549864

On Fri, Jul 17, 2009 at 10:24 PM, David Calavera <david.calavera@...> wrote:

I'm not sure if that's what you want to do, but I think you have to declare the class to extend with the fully qualified name. This works for me, from jirb:

irb(main):022:0> module Util

irb(main):023:1>  include_package 'java.util'

irb(main):024:1> 

irb(main):025:1*  class Java::JavaUtil::ArrayList

irb(main):026:2>     def baz

irb(main):027:3>       size

irb(main):028:3>     end

irb(main):029:2>  end

irb(main):030:1> end

irb(main):033:0> l = java.util.ArrayList.new     

=> #<Java::JavaUtil::ArrayList:0xe11a87 @java_object=#<Java::JavaObject:0x94cbe2>>

irb(main):034:0> l.add 5                    

=> true

irb(main):035:0> l.baz                      

=> 1

On Fri, Jul 17, 2009 at 10:05 PM, Timothy Hanson <thanson@...> wrote:

I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:

module Util
 include_package 'java.util'

 class ArrayList
    def baz
      size
    end
 end
end

l = Util::ArrayList.new
l.add 5 # <- This fails with "undefined method `add' for #<Util::ArrayList:0x16b61c3>"

Tim

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David Calavera
http://www.thinkincode.net

--
David Calavera
http://www.thinkincode.net

[Tim Hanson]

Some parts of this message have been removed. Learn more about Nabble's security policy.

What worked for me was to just reference the symbol in the module before extending it.

 

http://pastie.org/549942

 

Tim

 

From: David Calavera [mailto:david.calavera@...]
Sent: Friday, July 17, 2009 1:37 PM
To: user@...
Subject: Re: [jruby-user] include_package strangeness

 

So, if you want to use your namespace you have to extend the class outside the namespace definition, or at least it's how I do it, this is an example:

 

http://pastie.org/549864

On Fri, Jul 17, 2009 at 10:24 PM, David Calavera <david.calavera@...> wrote:

I'm not sure if that's what you want to do, but I think you have to declare the class to extend with the fully qualified name. This works for me, from jirb:

 

irb(main):022:0> module Util

irb(main):023:1>  include_package 'java.util'

irb(main):024:1> 

irb(main):025:1*  class Java::JavaUtil::ArrayList

irb(main):026:2>     def baz

irb(main):027:3>       size

irb(main):028:3>     end

irb(main):029:2>  end

irb(main):030:1> end

 

irb(main):033:0> l = java.util.ArrayList.new     

=> #<Java::JavaUtil::ArrayList:0xe11a87 @java_object=#<Java::JavaObject:0x94cbe2>>

irb(main):034:0> l.add 5                    

=> true

irb(main):035:0> l.baz                      

=> 1

 

On Fri, Jul 17, 2009 at 10:05 PM, Timothy Hanson <thanson@...> wrote:

I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:

module Util
 include_package 'java.util'

 class ArrayList
    def baz
      size
    end
 end
end

l = Util::ArrayList.new
l.add 5 # <- This fails with "undefined method `add' for #<Util::ArrayList:0x16b61c3>"

Tim

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David Calavera
http://www.thinkincode.net

--
David Calavera
http://www.thinkincode.net

[Charles Oliver Nutter-4]

On Fri, Jul 17, 2009 at 3:05 PM, Timothy
Hanson<thanson@...> wrote:
> I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:

Yeah, this is a known limitation of include_package. Since it just
installs a const_missing hook, it's subject to constant lookup
behaviors. In this case, it does not fire the hook when you just open
a class, because you could honestly just be defining a new class.

Your workaround of referencing the classes first is a pretty good
solution. We've also hoped that some day we could include a package
indexing tool that eagerly defines the constants, but that has never
happened. If someone wanted to try to integrate Jython's package
indexer, the code is available here:

http://code.google.com/p/jvm-language-runtime/source/browse/#svn/trunk/packagecache

- Charlie

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[gin]

Sorry for joining the ancient thread now - just noticed it.

> referencing the classes first is a pretty good solution

I think the best way to deal with this is the same as for extending
classes that we know exist already: use class_eval.
It can hit 2 birds with 1 stone: 1) should work safely with
include_package,  2) in general, it will complain if you were
"extending" the wrong class by mistake (which IMHO is a common annoyance).

So:
MyJavaClass.class_eval do
    def my_extension
    end
end

rather than:

class MyJavaClass
    def my_extension
    end
end

Gergo

2009/7/21 Charles Oliver Nutter <headius@...>:

> On Fri, Jul 17, 2009 at 3:05 PM, Timothy
> Hanson<thanson@...> wrote:
>> I'm extending Java classes in Ruby, but there's one odd catch. I use include_package to pull the whole Java package into a Ruby module. The problem is that the classes are defined lazily, so if my extension is defined before the Java entity is referenced, rather than "extending" the java class, I hide it. Eg:
>
> Yeah, this is a known limitation of include_package. Since it just
> installs a const_missing hook, it's subject to constant lookup
> behaviors. In this case, it does not fire the hook when you just open
> a class, because you could honestly just be defining a new class.
>
> Your workaround of referencing the classes first is a pretty good
> solution. We've also hoped that some day we could include a package
> indexing tool that eagerly defines the constants, but that has never
> happened. If someone wanted to try to integrate Jython's package
> indexer, the code is available here:
>
> http://code.google.com/p/jvm-language-runtime/source/browse/#svn/trunk/packagecache
>
> - Charlie
>
> ---------------------------------------------------------------------
> To unsubscribe from this list, please visit:
>
>    http://xircles.codehaus.org/manage_email
>
>
>

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