In Ruby, why does Array.new(size, object) create an array consisting of multiple references to the same object?

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Because that’s what the documentation says it does. Note that Hash.new is only being called once, so of course there’s only one Hash

If you want to create a new object for every element in the array, pass a block to the Array.new method, and that block will be called for each new element:

>> a = Array.new(2) { Hash.new }
=> [{}, {}]
>> a[0]['cat'] = 'feline'
=> "feline"
>> a
=> [{"cat"=>"feline"}, {}]
>> a[1]['cat'] = 'Felix'
=> "Felix"
>> a
=> [{"cat"=>"feline"}, {"cat"=>"Felix"}]

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