From: Robert Klemme <bob.news@...>
Date: 2005-09-24T23:21:40+09:00
Subject: Re: OpenClass

Doug Kearns <dougkearns@gmail.com> wrote:
> On Sat, Sep 24, 2005 at 04:41:40PM +0900, Robert Klemme wrote:
>
> <snip>
>
>> I don't see the advantange of this syntax over
>>
>> def o.test_method() puts "test_method" end
>>
>> Can you explain?
>
> Well, I guess it lets you do something like:
>
> name = "Robert"
> o = OpenClass.new
> o.test_method = %{ puts "Hello #{name}" }
> o.test_method

>> class Foo;end
=> nil
>> f = Foo.new
=> #<Foo:0x1018f060>
>> name = "robert"
=> "robert"
>> class <<f;self;end.instance_eval { define_method(:test_method) { puts 
>> name } }
=> #<Proc:0x10181440@(irb):47>
>> f.test_method
robert
=> nil

Not shorter or nicer but syntax checked on compile time.  It's usually 
better to try to avoid eval (some $SAFE levels even forbid eval if I'm not 
mistaken).  You can easily put the code above into a helper method in class 
Module so this becomes more convenient.

Kind regards

    robert