Swift：命名空间的使用

参照RxSwift写的命名空间

方法一：

/**
 /// A type that has reactive extensions.
 public protocol ReactiveCompatible {
     /// Extended type
     associatedtype ReactiveBase

     @available(*, deprecated, message: "Use `ReactiveBase` instead.")
     typealias CompatibleType = ReactiveBase

     /// Reactive extensions.
     static var rx: Reactive<ReactiveBase>.Type { get set }

     /// Reactive extensions.
     var rx: Reactive<ReactiveBase> { get set }
 }
 */
protocol MZCompatibleProtocol {
    associatedtype T
    static var mz: MZCompatible<T>.Type { get set }
    var mz: MZCompatible<T> { get }
}


/**
 extension ReactiveCompatible {
    /// Reactive extensions.
    public static var rx: Reactive<Self>.Type {
        get {
            return Reactive<Self>.self
        }
        set {
            // this enables using Reactive to "mutate" base type
        }
    }

    /// Reactive extensions.
    public var rx: Reactive<Self> {
        get {
            return Reactive(self)
        }
        set {
            // this enables using Reactive to "mutate" base object
        }
    }
}
*/
extension MZCompatibleProtocol {
    
    public static var mz: MZCompatible<Self>.Type {
        get {
            return MZCompatible<Self>.self
        }
        set { }
    }
    public var mz: MZCompatible<Self> {
        get {
            return MZCompatible<Self>(base: self)
        }
        set { }
    }
}


/**
 public struct Reactive<Base> {
     /// Base object to extend.
     public let base: Base

     /// Creates extensions with base object.
     ///
     /// - parameter base: Base object.
     public init(_ base: Base) {
         self.base = base
     }
 }
 */
public struct MZCompatible<Base> {
    /// Base object to extend.
    public let base: Base

    /// Creates extensions with base object.
    ///
    /// - parameter base: Base object.
    public init(base: Base) {
        self.base = base
    }
}


import class Foundation.NSObject
/// Extend NSObject with `mz` proxy.
extension NSObject: MZCompatibleProtocol { }

方法二：

/// 前缀
struct MZ<Base> {
    var base: Base
    init(_ base: Base) {
        self.base = base
    }
}

/// 利用协议扩展前缀
/// 协议扩展支持提供默认实现, 方便使其他类型支持前缀
protocol MZCompatible { }
extension MZCompatible {
    // 类型计算属性
    static var mz: MZ<Self>.Type {
        set { }
        get { MZ<Self>.self }
    }

    // 实例计算属性
    var mz: MZ<Self> {
        set { }
        get { MZ(self) }
    }
}

/// 给字符串扩展功能
extension String: MZCompatible { }
extension MZ where Base == String {
    var upperCount: Int {
        var count = 0
        for c in base where ("A"..."Z").contains(c) {
            count += 1
        }
        return count
    }
}

使用：
对UIColor进行扩展

import UIKit

extension MZCompatible where Base: UIColor {
    
    /// 获取随机颜色
    static func getRandomColor() -> UIColor {
        return UIColor(red: getArc4random(), green: getArc4random(), blue: getArc4random(), alpha: 1)
    }
    
    /// 获取随机数
    private static func getArc4random() -> CGFloat {
        return CGFloat(arc4random_uniform(256)) / 255.0
    }
}

调用：

view.backgroundColor = UIColor.mz.getRandomColor()