From: Martin DeMello <martindemello@...>
Date: 2008-10-09T02:09:13+09:00
Subject: [ruby-core:19211] Re: [Bug #622] merging nested hashes

On Wed, Oct 8, 2008 at 4:13 AM, izzet emre kutlu <redmine@ruby-lang.org> wrote:
>
> Shouldn't merge method return a new hash?
> Why is new hash referencing back to default[:opts] hash in this code?
>
> Is it a bug or is there something I am missing?

merge doesn't do a deep copy

irb> class A; attr_accessor :a; end
=> nil
irb> foo = A.new
=> #<A:0xb7cb813c>
irb> foo.a = 10
=> 10
irb> hash1 = {"foo" => foo, "bar" => "bar"}
=> {"foo"=>#<A:0xb7cb813c @a=10>, "bar"=>"bar"}
irb> hash2 = {"hello" => "world"}
=> {"hello"=>"world"}
irb> hash3 = hash1.merge(hash2)
=> {"foo"=>#<A:0xb7cb813c @a=10>, "hello"=>"world", "bar"=>"bar"}
irb> hash1
=> {"foo"=>#<A:0xb7cb813c @a=10>, "bar"=>"bar"}
irb> hash2
=> {"hello"=>"world"}
irb> hash3
=> {"foo"=>#<A:0xb7cb813c @a=10>, "hello"=>"world", "bar"=>"bar"}
irb> foo.a = 42
=> 42
irb> hash1
=> {"foo"=>#<A:0xb7cb813c @a=42>, "bar"=>"bar"}
irb> hash2
=> {"hello"=>"world"}
irb> hash3
=> {"foo"=>#<A:0xb7cb813c @a=42>, "hello"=>"world", "bar"=>"bar"}

martin