From: Demonic Software <demonic.software@...>
Date: 2008-03-13T15:07:25+09:00
Subject: Re: Setting Class Methods Using Strings

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Cool thanks Chris.

On Thu, Mar 13, 2008 at 12:50 AM, Chris Shea <cmshea@gmail.com> wrote:

> On Mar 12, 11:29 pm, Demonic Software <demonic.softw...@gmail.com>
> wrote:
> > [Note:  parts of this message were removed to make it a legal post.]
> >
> > 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.
>
> If you know when to use single quotes and when to use double quotes,
> yes to both:
>
>
> a = 1
> c = 'puts "a = #{a}"'   # => "puts \"a = \#{a}\""
> eval(c)                 # >> a = 1
>
> code = 'def foo_method(arg); puts "foo_method called with #{arg}";
> end'
> class Foo; end
> Foo.class_eval(code)
> Foo.new.foo_method('hi')  # >> foo_method called with hi
>
>
> Single-quoted strings do not perform interpolation, while double-
> quoted strings do. So if you juggle them for eval, you can have it do
> what you want. Of course, putting a backslash before the #{} in double-
> quoted strings will escape that so it doesn't perform the
> interpolation.
>
> Play around and you should get the hang of it quickly. And beware
> eval. Use carefully.
>
> HTH,
> Chris
>
>

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