From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-02-12T19:01:04+09:00
Subject: Re: Problem with array in hash

On Fri, Feb 12, 2010 at 10:50 AM, Sergey Sheypak
<serega.sheypak@gmail.com> wrote:
> require 'p'
>
> lol = {}
> lol[:arr] = []
> puts "#{lol[:arr].class} obj_id=#{lol[:arr].object_id}"
>
> lol[:arr] + [Task.new(:id => 'id01')]
> pp lol
> puts "#{lol[:arr].class} obj_id=#{lol[:arr].object_id}"
>
> lol[:arr] + [Task.new(:id => 'id02')]
> pp lol
> puts "#{lol[:arr].class} obj_id=#{lol[:arr].object_id}"
>
> lol[:arr] + [Task.new(:id => 'id03')]
> pp lol
> puts "#{lol[:arr].class} obj_id=#{lol[:arr].object_id}"
>
> Produces:
> Array obj_id=23293860
> {:arr=>[]}
> Array obj_id=23293860
> {:arr=>[]}
> Array obj_id=23293860
> {:arr=>[]}
> Array obj_id=23293860
> ---What does it mean? Nothin has been added

This is because the + method of Array doesn't modify the array, it
creates a new one:

irb(main):009:0> a = []
=> []
irb(main):010:0> a + [1,2,3]
=> [1, 2, 3]
irb(main):011:0> a
=> []
irb(main):012:0> a.object_id
=> -605891698
irb(main):013:0> (a + [1,2,3]).object_id
=> -605917598
irb(main):014:0> (a + [1,2,3]).object_id
=> -605928248


>
> lol = {}
> lol[:arr] = []
> lol[:arr] << Task.new(:id => 'id01')
> pp lol
> lol[:arr] << Task.new(:id => 'id02')
> pp lol
> lol[:arr] << Task.new(:id => 'id03')
> pp lol
>
>
>
> Produces:
> {:arr=>[Task[|id => id01|]]}
> {:arr=>[Task[|id => id02|], Task[|id => id02|]]}
> {:arr=>[Task[|id => id03|], Task[|id => id03|], Task[|id => id03|]]}
> ---Why does each insertion replaces each elem in array?

I don't know what happens in the Task constructor, because this works for me:

irb(main):001:0> Task = Struct.new :id
=> Task
irb(main):002:0> lol = {}
=> {}
irb(main):003:0> lol[:arr] = []
=> []
irb(main):005:0> lol[:arr] << Task.new(1)
=> [#<struct Task id=1>]
irb(main):006:0> lol[:arr] << Task.new(2)
=> [#<struct Task id=1>, #<struct Task id=2>]
irb(main):007:0> lol[:arr] << Task.new(3)
=> [#<struct Task id=1>, #<struct Task id=2>, #<struct Task id=3>]
irb(main):008:0> lol[:arr]
=> [#<struct Task id=1>, #<struct Task id=2>, #<struct Task id=3>]



>
> !!!but!!!
> arr = []
> arr << Task.new(:id => 'id01')
> pp arr
> arr << Task.new(:id => 'id02')
> pp arr
> arr << Task.new(:id => 'id03')
> pp arr
>
> produces:
> [Task[|id => id01|]]
> [Task[|id => id02|], Task[|id => id02|]]
> [Task[|id => id03|], Task[|id => id03|], Task[|id => id03|]]
> ---it's ok...

I don't see it ok, I see that it happens exactly the same as when the
array is in the hash. You must be doing something in the Task class
that messes with the instances or something. Can you show us the Task
class? Or show us, what do you get when you execute this:

a = Task.new(:id => 'id01')
p a
b = Task.new(:id => 'id02')
p b
p [a,b]


Jesus.