Ruby Array tricks

• Easily iterate through array of arrays:

[[:a, 100], [:b, 200]].each { |k, v| puts [k, v].inspect }
#=> [:a, 100]
#=> [:b, 200]

• Combined lambda arguments:

{a: 100, b: 200}.each_with_object({}) { |(k, v), h| puts [k, v, h].inspect }
#=> [:a, 100, {}]
#=> [:b, 200, {}]

• Convert hash to array with indexes:

{a: 100, b: 200}.map.with_index { |(k, v), i| [k, v, i] }
#=> [[:a, 100, 0], [:b, 200, 1]]

• Mega-combined lambda arguments and with_index example:

{a: 100, b: 200}.each_with_object({}).with_index { |((k, v), h), i| puts [k, v, h, i].inspect }
#=> [:a, 100, {}, 0]
#=> [:b, 200, {}, 1]

• Hide «unused variable» warning in IDE:

{a: 100, b: 200}.select { |_k, v| v == 200 }

• Convert array of arrays to hash:

[[:a, 100], [:b, 200]].to_h
#=> {:a=>100, :b=>200}