From: Brian Candler <lists@...>
Date: 2012-09-20T16:48:45+09:00
Subject: Re: the behavior of iterator methods

ten ten wrote in post #1076743:
> irb(main):001:0> s = ["a", "b", "c"]
> => ["a", "b", "c"]
> irb(main):002:0> s[0].object_id
> => 36971304
> irb(main):003:0> s[1].object_id
> => 36971292
> irb(main):004:0> s[2].object_id
> => 36971280
> irb(main):005:0> s.each{|c| c.upcase!}
> => ["A", "B", "C"]
> irb(main):006:0> p s
> ["A", "B", "C"]
> => nil

It may be instructive to compare:

s.each{|c| c << "X"}
s.each{|c| c += "X"}

The first mutates the object by adding a character to it. The second is 
short for c = c + "X"; it creates a new object from concatenating the 
two, and assigns the new object to local variable c. However it does not 
change the object which is still referenced from the array.

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