From: Rick DeNatale <rick.denatale@...>
Date: 2010-04-29T02:27:04+09:00
Subject: Re: Overload the normal behavior of an object/instance in string

On Wed, Apr 28, 2010 at 1:03 PM, Walle Wallen <walle.sthlm@gmail.com> wrote:
> Long story short. I'm trying to overload the normal behavior of an
> object/instance in a string. Instead of replying "<Test:0x101121db0>" I
> would like it too return a specific string, or something similar. I have
> tried to overload inspect, and it seems to work pretty well, except when
> using the object with puts or in a string "#{p}".
>
> My english ain't good, but I hope you understand the principle of what I
> am trying to achieve.

There are two different methods which Ruby uses to get a printstring
from an object, both of which should return a String.

inspect produces a 'programmer friendly' printstring in general, while
to_s produces a 'user friendly' string.

There's a Kernel method p which is roughly equvalent to:

def p(arg)
   puts arg.inspect
end

puts just uses to_s to convert non-strings to strings.

And irb displays the the value of inspect after evaluating an expression.


> [code]
> class Test
>  def inspect
>     puts "this is a test"
>  end

This should simply return the string, you don't always want to puts
the result, and puts will cause the result to be nil, not the string.
> end
>
> p = Test.new
> this is a test
>>> p
> this is a test
>
> puts p
> #<Test:0x101121db0>
>
>>> "#{p}"
> => "#<Hejsan:0x1010fd7f8>"
> [/code]

Try this:

class Test
 def inspect
    "this is a test inspection"
 end

 def to_s
   "this is a test"
   end
end

p = Test.new
puts p
puts "#{p}"
puts p.inspect

which produces:

this is a test
this is a test
this is a test inspection


-- 
Rick DeNatale

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