Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.ruby > #3576 > unrolled thread

Help me understand this SIMPLE Ruby code, using puts in a def

Back to article view | Back to comp.lang.ruby

Contents

  Help me understand this SIMPLE Ruby code, using puts in a def Fily Salas <fs_tigre@hotmail.com> - 2011-04-27 15:25 -0500
    Re: Help me understand this SIMPLE Ruby code, using puts in a def Sam Duncan <sduncan@wetafx.co.nz> - 2011-04-27 15:35 -0500
    Re: Help me understand this SIMPLE Ruby code, using puts in a def Roger Braun <roger@rogerbraun.net> - 2011-04-27 15:41 -0500
    Re: Help me understand this SIMPLE Ruby code, using puts in a def Cee Joe <cyril_jose@ymail.com> - 2011-04-27 15:47 -0500
    Re: Help me understand this SIMPLE Ruby code, using puts in a def Fily Salas <fs_tigre@hotmail.com> - 2011-04-27 18:38 -0500

#3576 — Help me understand this SIMPLE Ruby code, using puts in a def

Hi,

I was practicing ruby and accidentally came across something that got me
thinking (nothing important but I want to know why).

Why does the example-1 works and not example-2, if all I'm doing is
moving the puts?

Example-1:
def message
  "this is working"
end
puts message.upcase


Example-2:
def message
  puts "this is working"
end
message.upcase

Can someone explain this a little bit? I could just ignore it but I
would like to know the reason.

Thanks

-- 
Posted via http://www.ruby-forum.com/.

[toc] | [next] | [standalone]

#3577

This is where irb is handy. The short of it is that in your first 
example a string is returned on which you call upcase. In your second 
example the thing returned is the result of puts, which is nil.

 > irb
ruby-1.9.2-p0 > foo = puts 'foo'
foo
  => nil
ruby-1.9.2-p0 > foo
  => nil
ruby-1.9.2-p0 > foo.upcase
NoMethodError: undefined method `upcase' for nil:NilClass

Does that help?

Sam


On 28/04/11 08:25, Fily Salas wrote:
> Hi,
>
> I was practicing ruby and accidentally came across something that got me
> thinking (nothing important but I want to know why).
>
> Why does the example-1 works and not example-2, if all I'm doing is
> moving the puts?
>
> Example-1:
> def message
>    "this is working"
> end
> puts message.upcase
>
>
> Example-2:
> def message
>    puts "this is working"
> end
> message.upcase
>
> Can someone explain this a little bit? I could just ignore it but I
> would like to know the reason.
>
> Thanks
>

[toc] | [prev] | [next] | [standalone]

#3578

Hi Fily

2011/4/27 Fily Salas <fs_tigre@hotmail.com>:
> Hi,
>
> I was practicing ruby and accidentally came across something that got me
> thinking (nothing important but I want to know why).
>
> Why does the example-1 works and not example-2, if all I'm doing is
> moving the puts?
>
> Example-1:
> def message
>  "this is working"
> end
> puts message.upcase
>
>
> Example-2:
> def message
>  puts "this is working"
> end
> message.upcase
>
> Can someone explain this a little bit? I could just ignore it but I
> would like to know the reason.

The return value of the "puts" method is always nil, not the string it
prints. What your second example does is try to invoke the "upcase"
method on nil.

-- 
Roger Braun
rbraun.net | humoralpathologie.de

[toc] | [prev] | [next] | [standalone]

#3579

I agree with Sam:

>> def message
>> "this is working"
>> end
=> nil
>> puts message.upcase
THIS IS WORKING
=> nil

>> def message1
>> puts "this is working"
>> end
=> nil
>> puts message1
this is working
nil               <----- extra nil
=> nil

Since the nil is the last thing that is read in the method, upcase is 
called on that nil and upcase throws an error b/c you can't use that 
method on a nil. Make sense?

-Cee

-- 
Posted via http://www.ruby-forum.com/.

[toc] | [prev] | [next] | [standalone]

#3589

Got it.  Thank you all very much for your help!

-- 
Posted via http://www.ruby-forum.com/.

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.ruby

csiph-web