From: Oliver Peng <oliver.peng@...>
Date: 2008-03-08T01:28:24+09:00
Subject: Re: the value in ensure block is not returned

Robert Klemme wrote:
> 2008/3/6, Oliver Peng <oliver.peng@skywave.com>:
>>  > Why should it?  If you think about it you will see that it's actually
>>  > Yes, no problem here.
>>
>>  irb(main):012:0> test
>>  => 2
>>
>>  It looks that the result value has been saved to a temp place before
>>  running ensure block. Is that correct?
> 
> The return value is determined the very moment the block ends, which
> means that the *reference* is saved (as always in Ruby).  But since
> you used Fixnums and simply reassigned to b ("b += 3") this won't be
> visible.  But
> 
> irb(main):001:0> def t
> irb(main):002:1> s="foo"
> irb(main):003:1> ensure
> irb(main):004:1* s.replace "see?"
> irb(main):005:1> end
> => nil
> irb(main):006:0> t
> => "see?"
> irb(main):007:0>
> 
> In other words, of course you can change the object before it is 
> returned.
> 
>>  irb(main):021:1> end
>>  => nil
>>  irb(main):023:0> test1
>>  => 3
>>  irb(main):024:0> @@value
>>  => 8
> 
> Same story: you reassigned.
> 
> Cheers
> 
> robert

Ok I see. If I want to change the return value in ensure block, I need 
to change the object itself in the last line before ensure, not just 
reassign the varialbe. I also write another test code which can 
demonstrate clearly:

irb(main):003:0> class A
irb(main):004:1> attr_accessor :value
irb(main):005:1> end
=> nil
irb(main):006:0> def test
irb(main):007:1> begin
irb(main):008:2* a = A.new
irb(main):009:2> a.value = 1
irb(main):010:2> a
irb(main):011:2> ensure
irb(main):012:2* a.value = 2
irb(main):013:2> end
irb(main):014:1> end
=> nil
irb(main):015:0> test
=> #<A:0xb7be48a0 @value=2>

I also did a test to try to do return in ensure block and it has higher 
priority. Here is my test code:

irb(main):022:0> def test
irb(main):023:1> begin
irb(main):024:2* a = 1
irb(main):025:2> a
irb(main):026:2> ensure
irb(main):027:2* return 2
irb(main):028:2> end
irb(main):029:1> end
=> nil
irb(main):030:0> test
=> 2

Finally I think the best way is to avoid returning value in ensure block 
and always put the return value in the last line of function or use 
return directly.

Thanks for your replay.
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