作为iOS整个项目的核心App delegate,随着项目的逐渐变大,会变得越来越臃肿,一不小心代码就过了千行.

大型项目的App delegate体积会大到什么程度呢?我们可以参考下国外2亿多月活的Telegram的 App delegate.是不是吓一跳,4千多行.看到这样的代码是不是很想点击左上角的x.

是时候该给App delegate解耦了,目标:

每个功能的配置或者初始化都分开,各自做各自的事情.App delegate要做到只需要调用就好了.

下面来谈谈如何利用两种设计模式实现:

1.命令模式

命令模式: 发送方发送请求,然后接收方接受请求后执行,但发送方可能并不知道接受方是谁，执行的是什么操作,这样做的好处是发送方和接受方完全的松耦合，大大提高程序的灵活性.

1. 定义好协议,把相关初始化配置代码分类

protocol Command {
    func execute()
}

struct InitializeThirdPartiesCommand: Command {
    func execute() {
        // 第三方库初始化代码
    }
}

struct InitialViewControllerCommand: Command {
    let keyWindow: UIWindow
    func execute() {
        // 根控制器设置代码
    }
}

struct InitializeAppearanceCommand: Command {
    func execute() {
        // 全局外观样式配置
    }
}

struct RegisterToRemoteNotificationsCommand: Command {
    func execute() {
        // 远程推送配置        
    }
}

2. 管理者

final class StartupCommandsBuilder {
    private var window: UIWindow!
    
    func setKeyWindow(_ window: UIWindow) -> StartupCommandsBuilder {
        self.window = window
        return self
    }
    
    func build() -> [Command] {
        return [
            InitializeThirdPartiesCommand(),
            InitialViewControllerCommand(keyWindow: window),
            InitializeAppearanceCommand(),
            RegisterToRemoteNotificationsCommand()
        ]
    }
}

3. App delegate调用

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        StartupCommandsBuilder()
            .setKeyWindow(window!)
            .build()
            .forEach { $0.execute() }
        
        return true
}

使用命令模式的好处是,如果要添加新的配置,设置完后只要加在StartupCommandsBuilder中就可以了.App delegate中不需要添加任何内容.

但这样做只能将didFinishLaunchingWithOptions中的代码解耦,App delegate中的其他方法怎样解耦呢?

2.组合模式

组合模式: 可以将对象组合成树形结构来表现”整体/部分”层次结构. 组合后可以以一致的方法处理个别对象以及组合对象.

这边我们给App delegate每个功能模块都设置一个子类,每个子类可以根据所需定义App delegate的方法.

1. 每个子模块实现各自的功能

// 推送
class PushNotificationsAppDelegate: AppDelegateType {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("推送配置")
        return true
    }
    
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        print("推送相关代码...")
    }
    
    // 其余方法
}

// 外观样式
class AppearanceAppDelegate: AppDelegateType {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("外观样式配置")
        return true
    }
}


// 控制器处理
class ViewControllerAppDelegate: AppDelegateType {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("根控制器设置代码")
        return true
    }
}


// 第三方库
class ThirdPartiesConfiguratorAppDelegate: AppDelegateType {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        print("第三方库初始化代码")
        return true
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        print("ThirdPartiesConfiguratorAppDelegate - applicationDidEnterBackground")
    }
    
    func applicationDidBecomeActive(_ application: UIApplication) {
        print("ThirdPartiesConfiguratorAppDelegate - applicationDidBecomeActive")
    }

}

2. 管理者

typealias AppDelegateType = UIResponder & UIApplicationDelegate

class CompositeAppDelegate: AppDelegateType {
    private let appDelegates: [AppDelegateType]

    init(appDelegates: [AppDelegateType]) {
        self.appDelegates = appDelegates
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        appDelegates.forEach { _ = $0.application?(application, didFinishLaunchingWithOptions: launchOptions) }
        return true
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        appDelegates.forEach { _ = $0.application?(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken) }
    }


    func applicationDidEnterBackground(_ application: UIApplication) {
        appDelegates.forEach { _ = $0.applicationDidEnterBackground?(application)
        }
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        appDelegates.forEach { _ = $0.applicationDidBecomeActive?(application)
        }
    }
}

3. App delegate调用

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    let appDelegate = AppDelegateFactory.makeDefault()

    enum AppDelegateFactory {
        static func makeDefault() -> AppDelegateType {
            
            return CompositeAppDelegate(appDelegates: [
                PushNotificationsAppDelegate(),
                AppearanceAppDelegate(),
                ThirdPartiesConfiguratorAppDelegate(),
                ViewControllerAppDelegate(),
                ]
            )
        }
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
         _ = appDelegate.application?(application, didFinishLaunchingWithOptions: launchOptions)
        return true
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        appDelegate.application?(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken)
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        appDelegate.applicationDidBecomeActive?(application)
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        appDelegate.applicationDidEnterBackground?(application)
    }
}

在App delegate解耦中相比命令模式,使用组合模式的可自定义程度会更高一点.

本文收录于 SwiftTips