‏map و compactMap

ما هي map؟

مثال بسيط على map

let numbers = [1, 2, 3, 4]
let doubled = numbers.map { $0 * 2 }
print(doubled)  // [2, 4, 6, 8]

تغيير نوع العنصر

let ids = [10, 20, 30]
let labels = ids.map { "ID-\($0)" }
print(labels)  // ["ID-10", "ID-20", "ID-30"]

استخدام map مع دالة مُسمّاة

let words = ["swift", "map"]
let upper = words.map { $0.uppercased() }
print(upper)  // ["SWIFT", "MAP"]

المشكلة التي لا يحلها map

هنا يأتي compactMap

let raw = ["1", "2", "x", "4"]
let nums = raw.compactMap { Int($0) }
print(nums)  // [1, 2, 4]  -- "x" was dropped

مقارنة مباشرة بين map و compactMap

let raw = ["1", "x", "3"]
print(raw.map { Int($0) })       // [Optional(1), nil, Optional(3)]
print(raw.compactMap { Int($0) }) // [1, 3]

فك تغليف القيم الاختيارية في مجموعة

let maybe: [Int?] = [1, nil, 3, nil, 5]
let clean = maybe.compactMap { $0 }
print(clean)  // [1, 3, 5]

تحليل البيانات باستخدام compactMap

let lines = ["42", "", "hello", "7"]
let values = lines.compactMap { Int($0) }
print(values)      // [42, 7]
print(values.reduce(0, +))  // 49

الجمع بين map و compactMap

let scores = ["90", "85", "n/a", "70"]
let passed = scores
    .compactMap { Int($0) }
    .map { $0 >= 80 ? "pass" : "fail" }
print(passed)  // ["pass", "pass", "fail"]

استخدام compactMap مع سلاسل القيم الاختيارية

struct User { let name: String? }
let users = [User(name: "Ann"), User(name: nil), User(name: "Bo")]
let names = users.compactMap { $0.name }
print(names)  // ["Ann", "Bo"]

اختبار سريع

مراجعة