From: Todd Benson <caduceass@...>
Date: 2008-03-13T16:14:03+09:00
Subject: Re: Setting Class Methods Using Strings

On Thu, Mar 13, 2008 at 12:29 AM, Demonic Software
<demonic.software@gmail.com> wrote:
> Hello,
>
>  First question:
>  With the 'print 'foo_method called with \#{arg}', is there a way to escape
>  the "#" so that arg will not be evaluated until after the statement is
>  evalled?  For example:
>
>  Let c be "'print 'foo_method called with \#{arg}'"
>
>  eval(c) => print 'foo_method called with #{arg}'
>
>
>
>  Second (Main Question)
>  Is it possible to set an object's methods with raw code and a method name?
>  I am not sure how to Google for an example on this, so I will just show an
>  example.
>
>  == Here is an empty class definition Foo, and later on I will want to
>  assign/add/set a method in an instantiated Foo object ==
>
>  class Foo
>  end
>
>  == Now I want to set a method in an instantiated Foo with  code, so that I
>  can call f ==
>
>  code = "def foo_method(arg)
>                print 'foo_method called with #{arg}'
>             end"
>
>  f = Foo.new()
>  #...
>  #code to set a method in f
>  #...
>
>  f.foo_method("for the win!")
>
>  ==
>
>  Is this possible?  or Do I need create a string and add the method in like
>  the following example?
>
>  code = "\ndef foo_method(arg)
>                print 'foo_method called with \#{arg}'
>             end\n"
>  foo = "class Foo " + code + " end"
>
>  eval(foo)
>  f = Foo.new()
>  f.foo_method("for the win!")
>
>
>
>  Thanks in advance for your help.

Unless you absolutely _have_ to create a string (like you're holding
code in a database that is to be executed)...

class Foo
end

f = Foo.new
g = Foo.new

def f.bar arg; puts arg; end

f.bar "hi"
# "hi"
g.bar "hi"
# undefined method error

It can also be done like this after the class construction...

class << f
  def bar arg; puts arg; end
end

I don't think this case is a good use of #eval, but it depends on what
you're doing.

hth,
Todd