Ruby 2D Array Assignment Possible Bug? -


i'm experiencing following. expect first sub-element of first sub array assigned "x", not first element of each sub array. can explain behaviour, , perhaps how work around it? (note may expected behaviour, if is, contradicts expectations.)

x = array.new(3, array.new(5)) # => [[nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil]] x[0][0] # => nil x[0][0] = "x" x # => [["x", nil, nil, nil, nil], ["x", nil, nil, nil, nil], ["x", nil, nil, nil, nil]]

workaround :

x = array.new(3) { array.new(5) } x[0][0] = 'a' x # => [["a", nil, nil, nil, nil], [nil, nil, nil, nil, nil], [nil, nil, nil, nil, nil]]

new(size) {|index| block }

here array of given size created. each element in array created passing element’s index given block , storing return value.

read common gotchas

when sending second parameter, same object used value array elements. since array elements store same array array.new(5), changes 1 of them affect them all.

if multiple copies want, should use block version uses result of block each time element of array needs initialized, did above.


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