用更 Swifty 的代码遍历数据.swift

import UIKit

extension SequenceType {
    /// flatMap 出我们需要的类型
    ///
    /// - Complexity: O(*M* + *N*), where *M* is the length of `self`
    ///   and *N* is the length of the result.
    @warn_unused_result
    public func flatMap<T>(type type: T.Type) -> [T] {
        return flatMap { $0 as? T }
    }
}

public protocol OptionalType {
    associatedtype Wrapped
    var value: Wrapped? { get }
}

extension Optional: OptionalType {
    /// Cast `Optional<Wrapped>` to `Wrapped?`
    public var value: Wrapped? {
        return self
    }
}

extension SequenceType where Generator.Element: OptionalType {
    
    @warn_unused_result
    public func filterNil() -> [Generator.Element.Wrapped] {
        return self.flatMap { $0.value }
    }
    
    @warn_unused_result
    public func withoutNil() -> [Generator.Element.Wrapped] {
        return self.flatMap { $0.value }
    }
}

var array: [Int?] = [1, 2, 3, 4, nil, 6]

print("\nif let")

for value in array { // 这里的 value 是 Int? 类型
    if let value = value {
        print(value) // 这里的 value 是 Int 类型
    }
}

print("\nwhere")

for value in array where value != nil { // 这里的 value 是 Int? 类型
    print(value!) // 这里的 value 是 Int? 类型
}

print("\nfilter")

for value in array.filter({ $0 != nil }) { // 这里的 value 是 Int? 类型
    print(value!) // 这里的 value 是 Int? 类型
}

print("\nwithoutNil")

for value in array.withoutNil() { // 这里的 value 是 Int 类型
    print(value) // 这里的 value 是 Int 类型
}

print("\nflatMap UIButton")

let view = UIView()

view.addSubview(UIView())
view.addSubview(UIView())

view.addSubview(UIButton(type: .System))
view.addSubview(UIButton(type: .System))

for button in view.subviews.flatMap(type: UIButton.self) { // 这里的 button 是 UIButton 类型
    print(button) // yooo 直接就是 UIButton 了
}

struct Phone {
    var number: String?
    var originalLabel: String?
    
    init(number: String? = nil, originalLabel: String? = nil) {
        self.number = number
        self.originalLabel = originalLabel
    }
}

struct User {
    var name: String?
    var phones: [Phone]?
    
    init(name: String? = nil, phones: [Phone]? = nil) {
        self.name = name
        self.phones = phones
    }
}

let user1 = User(name: "user1", phones: nil)
let user2 = User(name: nil, phones: [Phone(number: "110")])
let user3 = User(name: "user3", phones: [Phone(number: "120"), Phone(number: "1201")])
let user4 = User(name: "user4", phones: [Phone(number: "140")])

typealias UploadContact = [String: String]

[user1, user2, user3, user4]
    .flatMap { user -> (name: String, numbers: [String])? in
        guard let name = user.name, phones = user.phones else { return nil }
        return (name: name, numbers: phones.flatMap { $0.number })
    }
    .flatMap { contact -> [UploadContact] in
        return contact.numbers.map { ["name": contact.name, "number": $0] }
    }

其实好想问为啥你能想到这样写？

@zyg-github ^^ 因为懒