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rubyobjectcopyclone

Cloning an array with its content

I want to make a copy of an array, to modify the copy in-place, without affecting the original one. This code fails

a = [
  '462664',
  '669722',
  '297288',
  '796928',
  '584497',
  '357431'
]
b = a.clone
b.object_id == a.object_id # => false
a[1][2] = 'X'
a[1] #66X722
b[1] #66X722

The copy should be different than the object. Why does it act like if it were just a reference?

Solution

  • You need to do a deep copy of your array.

    Here is the way to do it 

    Marshal.load(Marshal.dump(a))

    This is because you are cloning the array but not the elements inside. So the array object is different but the elements it contains are the same instances. You could, for example, also do a.each{|e| b << e.dup} for your case