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Without using index I was able to destructure the first and second elements of an Array of Arrays like so:

[ [ 1, 2 ], [ 3, 4 ] ].each do |first, second|
  puts second
end
#=> 2
#=> 4

I then needed to get the index for each iteration so I used .with_index and I assumed the index would just get added as the last argument of the block:

[ [ 1, 2 ], [ 3, 4 ] ].each.with_index do |first, second, index|
  puts second
end
#=> 0
#=> 1

However, it was the index. The first value is the entire Array, not destructured.

How do you use .with_index and still destructure the Array?

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1 Answer 1

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4

You can destructure by passing parentheses to the first argument and that will destructure as before and keep the index as the second argument:

[ [ 1, 2 ], [ 3, 4 ] ].each.with_index do |( first, second ), index|
  puts second
end
#=> 2
#=> 4
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1 Comment

Just as (first, second), idx = [[[1,2], [3,4]], 2] produces first #=> [1,2], second #=> [3,4], idx #=> 2. See the doc for Array Decomposition.

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