要点 Swiftではmap, filter, flatMap, forEachを使えばfor文は必要ありません。 mapの例 let numbers: [Int] = [1, 2, 3] // for文 var twice = [Int]() for num in numbers { twice.append(num * 2) } // map let twice = numbers.map { $0 * 2 } // twice = [2, 4, 6] filterの例 let numbers: [Int] = [1, 2, 3] // for文 var odd = [Int]() for num in numbers { if num % 2 != 0 { odd.append(num) } } // filter let odd = numbers.filter { $0 % 2 !