one more thing Flat Map

let nestedArray = [[1,2,3], [4,5,6]]let flattenedArray = nestedArray.flatMap { $0 }flattenedArray // [1, 2, 3, 4, 5, 6]

or

var multipliedFlattenedArray = nestedArray2.flatMap { $0.map 
      { $0 * 2 } 
}