From: Brian Candler <b.candler@...>
Date: 2009-05-27T06:18:25+09:00
Subject: Re: saving values in block problem

Peng Zuo wrote:
> Hi,I'm using ruby 1.87. this problem seems to be the block context bug 

http://www.catb.org/~esr/faqs/smart-questions.html#id306810

Does this explain what you are seeing?

irb(main):001:0> a = []
=> []
irb(main):002:0> str = "xxx"
=> "xxx"
irb(main):003:0> a << str
=> ["xxx"]
irb(main):004:0> str << "yyy"
=> "xxxyyy"
irb(main):005:0> a << str
=> ["xxxyyy", "xxxyyy"]
irb(main):006:0> str << "zzz"
=> "xxxyyyzzz"
irb(main):007:0> a << str
=> ["xxxyyyzzz", "xxxyyyzzz", "xxxyyyzzz"]
irb(main):008:0> a
=> ["xxxyyyzzz", "xxxyyyzzz", "xxxyyyzzz"]
irb(main):009:0>

An array only holds references to objects. If you insert a reference to 
the same object multiple times into the array, then you will simply see 
the same object multiple times.

As for why 'dup' doesn't work: you'll need to show your code. If you are 
maintaining state in an instance variable, dup should work. If you are 
maintaining state indirectly - the instance variable points to some 
other object which in turn holds state - then the dup'd object will 
still point to this same object.
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