From: "David A. Black" <dblack@...>
Date: 2008-04-03T15:57:00+09:00
Subject: Re: nested ruby

Hi --

On Thu, 3 Apr 2008, Sunil Chikkegowda wrote:

> Hello All,
>
> Take a look at this example:
>
> def method1
>  puts 'hello'
>  def method2
>    puts 'world'
>  end
> end
>
> In IRB, if I say 'method1' it gives 'hello' as output. For
> 'method1.method2' it gives 'hello' in first line and 'world' in second
> line.
>
> My question is: Is there any way to print only 'world' if I execute
> method1.method2

Given the above definition, you can't execute method1 without having
it print 'hello'. The fact that method2 prints 'world' is totally
unconnected -- in fact, method1 and method2 are unconnected. When you
do method1.method2, you're actually calling method2 on nil (the return
value of method1).

You can see this from a slightly different angle here:

irb(main):007:0> def nil.m2
irb(main):008:1>   "Calling nil.m2"
irb(main):009:1> end
=> nil
irb(main):010:0> def m1
irb(main):011:1>   def m2
irb(main):012:2>     super
irb(main):013:2>   end
irb(main):014:1> end
=> nil
irb(main):015:0> m1.m2
=> "Calling nil.m2"

You can tell that the call to m2 on line 15 has nil as its receiver,
because it successfully finds the "super" version that was defined on
line 7.


David

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