From: Lars Christensen <larsch@...>
Date: 2001-08-17T01:31:07+09:00
Subject: [ruby-talk:19908] Re: The GUI poll is in, and the resultsaresurprising

On Fri, 17 Aug 2001, Hal E. Fulton wrote:

> > module Fox
> >   class FXMainWindow
> >     def FXMainWindow.identifier(*symbols)
> >       instance_eval "#{symbols.join ', '}, ID_LAST =
> >          enum(Fox::FXMainWindow::ID_LAST, #{symbols.length + 1})"
> >     end
> >   end
> > end
>
> Hmm. Can you explain this?

Basically, it is a wrapper around the original approach. It builds a
string like you would otherwise have to do yourself and evaluates it. Here
is an example of a custom instance variable declarator, equivalent to
attr_reader:

class Module
  def myattr_reader(*symbols)
    symbols.each { |sym|
      module_eval %Q{
        def #{sym}
          @#{sym}
        end
      }
    }
  end
end

class Foo
  myattr_reader :bar, :baz
  def initialize
    @bar = 2
  end
end

f = Foo.new
p f.bar       #=> 2
p f.baz       #=> nil

> > > If some future version of Ruby supports keyword arguments, the situation
> > > will be even better.
> >
> > Great! By why keep the arguments if you can do without them. When you use
> > them, the expression becomes unreadable. You still won't be able to
> > remember with the 5th argument was about. The only exception is the use of
> > named arguments (by symbol or string, which is possible with today's
> > ruby!):
>
> When Lyle said "keyword arguments" he meant the same as you mean
> by "named arguments."

Not exactly, but its close. If I am not mistaken, keyword arguments will
allow this code:

  def func(size = 10, weight = 20, color = 'red')
     ...
  end
  func(weight => 10, color => 'blue')

While, with current ruby, you would have to do this:

  def func(hashargs)
    size = hashargs[:size] || 10
    weight = hashargs[:weight] || 20
    color = hashargs[:color] || 'red'
    ...
  end

  func(:weight => 10, :color => 'blue')

Which is not as nice as keyword arguments :-)

-- 
Lars Christensen, larsch@cs.auc.dk