小编wer*_*ver的帖子

在Swift 中有关联类型这样的概念。

protocol Container {
    associatedtype ItemType // Here it is.
    mutating func append(item: ItemType)
    var count: Int { get }
    subscript(i: Int) -> ItemType { get }
}

struct IntStack: Container {
    typealias ItemType = Int // Here again.
    mutating func append(item: Int) {
        self.push(item)
    }
    var count: Int {
        return items.count
    }
    subscript(i: Int) -> Int {
        return items[i]
    }

    var items = [Int]()
    mutating func push(item: Int) {
        items.append(item)
    }
    mutating func pop() …

我对Swift中灵活的通用服务定位器设计模式实现感兴趣.

一种天真的方法可能如下:

// Services declaration

protocol S1 {
    func f1() -> String
}

protocol S2 {
    func f2() -> String
}

// Service Locator declaration
// Type-safe and completely rigid.

protocol ServiceLocator {
    var s1: S1? { get }
    var s2: S2? { get }
}

final class NaiveServiceLocator: ServiceLocator {
    var s1: S1?
    var s2: S2?
}

// Services imlementation

class S1Impl: S1 {
    func f1() -> String {
        return "S1 OK"
    }
}

class S2Impl: S2 {
    func …

我看到了许多private init在Swift中使用来限制对象构造的引用(例如这个),但是当我尝试时(在Xcode 7.2.1 Playground中)它似乎不可能:

class C {
    private init() {}
}

var c = C() // No errors.

我错过了什么或这实际上是一个错误吗？

我观看了"Swift中面向协议的编程"并阅读了相关的文档,但我仍然认为以下示例代码存在冲突(在Playground中尝试).

protocol X {

    // The important part is "static" keyword
    static var x: String { get }
}

extension X {
    // Here "static" again
    static var x: String {
        get {
            return "xxx"
        }
    }
}

// Now I'm going to use the protocol in a class, BUT
// in classes "static" is like "final class",
// i.e. CAN'T BE OVERRIDDEN, right?

// But I'd prefer to have the ability to override that property,
// so …