From: brabuhr@...
Date: 2010-08-04T03:35:50+09:00
Subject: Re: Remove the error

On Tue, Aug 3, 2010 at 2:07 PM, Amir Ebrahimifard <amiref@ymail.com> wrote:
> Why these codes result error ?
>
> 2-
> array = [*1..10]
> sum = array.inject { |memo,item| puts memo+item }

irb(main):001:0> array = [*1..10]
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
irb(main):002:0> sum = array.inject { |memo,item| puts memo+item }
3
NoMethodError: undefined method `+' for nil:NilClass
	from (irb):2
	from (irb):2:in `inject'
	from (irb):2:in `each'
	from (irb):2:in `inject'
	from (irb):2
	from :0

The method 'puts' always returns 'nil':

irb(main):003:0> sum = array.inject { |memo,item| puts "#{memo}\t#{item}" }
1	2
	3
	4
	5
	6
	7
	8
	9
	10
=> nil

irb(main):004:0> sum = array.inject { |memo,item| puts
"#{memo}\t#{item}\t#{memo + item}" }
1	2	3
NoMethodError: undefined method `+' for nil:NilClass
	from (irb):4
	from (irb):4:in `inject'
	from (irb):4:in `each'
	from (irb):4:in `inject'
	from (irb):4
	from :0