http://www.cocoachina.com/ios/20151117/14167.html
简介
在iOS工程中，AppDelegate往往会有上千行，甚至几千行，这样就会给维护AppDelegate带来诸多麻烦。比方说，老板想在出现HomeViewController之前弹出广告并停顿几秒，这样你就要加入插入广告的逻辑；又比方说，老板想在开始做个请求，判断某个开关是否打开。这样就会在AppDelegate中插入很多相关的不相关的代码。
在AppDelegate中，- (BOOL)application:(UIApplication )application didFinishLaunchingWithOptions:(NSDictionary )launchOptions是“Tells the delegate when the application has launched and may have additional launch options to handle.”，即在app开始运行时会调用里面的方法。在didFinishLaunchingWithOptions中，我们往往会渲染window，注册第三方监控库，加入基本页面跳转逻辑。
下面是一个常见项目中的didFinishLaunchingWithOptions：
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// objective-c语言- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { if (!([ADeanUserDataManager sharedManager].userName != nil && [ADeanUserDataManager sharedManager].userName.length > 0 && [ADeanUserDataManager sharedManager].userPassword != nil && [ADeanUserDataManager sharedManager].userPassword.length > 0)) { // 用户名、密码为空时候强制为未登录 [ADeanUserDataManager sharedManager].isUserLogined = @NO; } self.window.rootViewController = self.tabbarController; [self.window makeKeyAndVisible]; // 基本页面跳转逻辑 /*--------------------------------------*/ if ([[ADeanUserDataManager sharedManager].everLaunched boolValue] == NO) { //是否是第一次启动判断 [ADeanUserDataManager sharedManager].everLaunched = [NSNumber numberWithBool:YES]; [self.window addSubview:self.helpViewController.view]; } /*--------------------------------------*/ // 注册第三方库 /*--------------------------------------*/ // 注册Crash统计 -- Crashlytics [Fabric with:@[[Crashlytics class]]]; [MobClick startWithAppkey:UMENG_APPKEY]; [MobClick setCrashReportEnabled:NO]; // 关掉MobClick Crash Report收集开关#ifdef ADeanForTest [MobClick setCrashReportEnabled:YES]; // 打开MobClick Crash Report收集开关 [MobClick setLogEnabled:YES];#endif [ShareSDK registerApp:ShareSDKAppKey]; //新浪 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri]; //新浪微博客户端应用 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri weiboSDKCls:[WeiboSDK class]]; #if TARGET_IPHONE_SIMULATOR#else //QQ好友 [ShareSDK connectQQWithQZoneAppKey:QZoneAppKey qqApiInterfaceCls:[QQApiInterface class] tencentOAuthCls:[TencentOAuth class]];#endif //微信朋友圈 [ShareSDK connectWeChatSessionWithAppId:WeiXinAppID wechatCls:[WXApi class]]; //微信好友 [ShareSDK connectWeChatTimelineWithAppId:WeiXinAppID wechatCls:[WXApi class]]; [MiPushSDK registerMiPush:self type:(UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert) connect:YES]; /*--------------------------------------*/ // 其他逻辑 [self registerRemotePushNotification]; [self getSwitchInfoFromService]; [self appIntegrityCheck]; [self appSecurityCheck] ...... return YES;} |
下面我们就来看看，有什么好的办法可以对AppDelegate进行瘦身，加强代码的可读性和可维护性，并将代码放到适当的地方。
函数模块化
上述didFinishLaunchingWithOptions中可以按照功能逻辑划分为：处理启动逻辑，注册第三方库，处理其他逻辑三类。这样就可以优化为：
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// objective-c语言- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { if (!([ADeanUserDataManager sharedManager].userName != nil && [ADeanUserDataManager sharedManager].userName.length > 0 && [ADeanUserDataManager sharedManager].userPassword != nil && [ADeanUserDataManager sharedManager].userPassword.length > 0)) { // 用户名、密码为空时候强制为未登录 [ADeanUserDataManager sharedManager].isUserLogined = @NO; } self.window.rootViewController = self.tabbarController; [self.window makeKeyAndVisible]; // 基本页面跳转逻辑 [self baseViewJumpLogic]; // 注册第三方库 [self registThirdPart]; // 其他逻辑 [self handleOtherLogic] return YES;}- (void)baseViewJumpLogic { if ([[ADeanUserDataManager sharedManager].everLaunched boolValue] == NO) { //是否是第一次启动判断 [ADeanUserDataManager sharedManager].everLaunched = [NSNumber numberWithBool:YES]; [self.window addSubview:self.helpViewController.view]; }}- (void)registThirdPart { // 注册Crash统计 -- Crashlytics [Fabric with:@[[Crashlytics class]]]; [MobClick startWithAppkey:UMENG_APPKEY]; [MobClick setCrashReportEnabled:NO]; // 关掉MobClick Crash Report收集开关#ifdef ADeanForTest [MobClick setCrashReportEnabled:YES]; // 打开MobClick Crash Report收集开关 [MobClick setLogEnabled:YES];#endif [ShareSDK registerApp:ShareSDKAppKey]; //新浪 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri]; //新浪微博客户端应用 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri weiboSDKCls:[WeiboSDK class]]; #if TARGET_IPHONE_SIMULATOR#else //QQ好友 [ShareSDK connectQQWithQZoneAppKey:QZoneAppKey qqApiInterfaceCls:[QQApiInterface class] tencentOAuthCls:[TencentOAuth class]];#endif //微信朋友圈 [ShareSDK connectWeChatSessionWithAppId:WeiXinAppID wechatCls:[WXApi class]]; //微信好友 [ShareSDK connectWeChatTimelineWithAppId:WeiXinAppID wechatCls:[WXApi class]]; [MiPushSDK registerMiPush:self type:(UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert) connect:YES];}- (void)handleOtherLogic { [self registerRemotePushNotification]; [self getSwitchInfoFromService]; [self appIntegrityCheck]; [self appSecurityCheck] ......} |
模块化后，代码瞬间变得易读很多，而且需要改什么可以直接去相应的模块添加。但是这个仅仅是将代码的顺序变化下，相同功能的代码抽到一个函数中，代码行数没有减少，所有的功能还是糅合在一个.m中。
类模块化
很多其他逻辑是业务逻辑的，可以抽离到业务Model中，通过类模块化便捷使用。这样就可以优化为：
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// objective-c语言#import "ADeanAppCheck.h"#import "ADeanSwitches.h"- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { if (!([ADeanUserDataManager sharedManager].userName != nil && [ADeanUserDataManager sharedManager].userName.length > 0 && [ADeanUserDataManager sharedManager].userPassword != nil && [ADeanUserDataManager sharedManager].userPassword.length > 0)) { // 用户名、密码为空时候强制为未登录 [ADeanUserDataManager sharedManager].isUserLogined = @NO; } self.window.rootViewController = self.tabbarController; [self.window makeKeyAndVisible]; // 基本页面跳转逻辑 [self baseViewJumpLogic]; // 注册第三方库 [self registThirdPart]; // 其他逻辑 [self handleOtherLogic] return YES;}- (void)handleOtherLogic { [ADeanAppCheck appInfoCheck]; // Integrity & Security Check [ADeanSwitches appSwitchInit]; // Get Switch From Service ......} |
分类模块化
先抛个问题：分类中是否可以定义变量？
如果不知道可以参考：iOS分类中通过runtime添加动态属性
分类能够做到的事情主要是：即使在你不知道一个类的源码情况下，向这个类添加扩展的方法。这里我们主要是将对外开放的方法和一部分变量拿到分类中处理。这样进一步轻量化AppDelegate本身进行代码量。
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// objective-c语言// ADeanAppDelegate+Light.h文件#import "AppDelegate.h"@interface ADeanAppDelegate (Light)@property (nonatomic, strong) UITabbarController *tabbarController;/*! @brief 全局appDeleaget */+ (AppDelegate *)appDelegate;/*! @method @brief 关闭系统键盘 */+ (void)closeKeyWindow;@end// objective-c语言// ADeanAppDelegate+Light.m文件#import "ADeanAppDelegate+Light.h"- (UITabbarController *)tabbarController { UITabbarController *tabbarController = objc_getAssociatedObject(self, &kTabbarControllerObjectKey); if (!tabbarController) { tabbarController = [[UITabbarController alloc] init]; objc_setAssociatedObject(self, &kTabbarControllerObjectKey, tabbarController, OBJC_ASSOCIATION_RETAIN_NONATOMIC); } return tabbarController;}- (void)setTabbarController:(UITabbarController *)tabbarController { objc_setAssociatedObject(self, &kTabbarControllerObjectKey, tabbarController, OBJC_ASSOCIATION_RETAIN_NONATOMIC);}+ (AppDelegate *)appDelegate { return (AppDelegate *)[[UIApplication sharedApplication] delegate];}+ (void)closeKeyWindow { [[UIApplication sharedApplication].keyWindow endEditing:YES];}这样在AppDelegate中，对外开放的方法和部分变量可以抽离到分类中去。也可以根据作用定义不同的AppDelegate分类：#“ADeanAppDelegate+View.h”#“ADeanAppDelegate+Controller.h”#“ADeanAppDelegate+Method.h”… |
这样代码结构会更加清晰明了。 抽出来的AppDelegate只剩下注册第三方库了，因为第三方库很多是需要在didFinishLaunchingWithOptions中运行，正常的方法就很难。
Method Swizzling化
Method Swizzling是改变一个selector的实际实现的技术，关于Method Swizzling的概念、原理谷歌一堆。
Method Swizzling中以viewWillAppear为例，讲解了Method Swizzling的基本用法。
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#import "ADeanAppDelegate+Hook.h"#import "ADeanMethodSwizzling.h"#import "MobClick.h"#import "WXApi.h"#import "WeiboSDK.h"#import #import #import #if TARGET_IPHONE_SIMULATOR#else#import #import #import #endif@implementation ADeanAppDelegate (Hook)+ (void)initialize{ static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ [self adean_AppDelegateHook]; });}+ (void)adean_AppDelegateHook{ SwizzlingMethod([ADeanAppDelegate class], @selector(application:didFinishLaunchingWithOptions:), @selector(adean_application:didFinishLaunchingWithOptions:)); SwizzlingMethod([ADeanAppDelegate class], @selector(application:handleOpenURL:), @selector(adean_application:handleOpenURL:)); SwizzlingMethod([ADeanAppDelegate class], @selector(application:openURL:sourceApplication:annotation:), @selector(adean_application:openURL:sourceApplication:annotation:)); SwizzlingMethod([ADeanAppDelegate class], @selector(applicationDidReceiveMemoryWarning:), @selector(adean_applicationDidReceiveMemoryWarning:));}#pragma mark - Method Swizzling- (BOOL)adean_application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // 耗时的操作 // 注册Crash统计 -- Crashlytics [Fabric with:@[[Crashlytics class]]]; // 友盟统计 [MobClick startWithAppkey:UMENG_APPKEY]; [MobClick setCrashReportEnabled:NO]; // 关掉MobClick Crash Report收集开关#ifdef ADeanForTest [MobClick setCrashReportEnabled:YES]; // 打开MobClick Crash Report收集开关 [MobClick setLogEnabled:YES];#endif [ShareSDK registerApp:ShareSDKAppKey]; //新浪 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri]; //新浪微博客户端应用 [ShareSDK connectSinaWeiboWithAppKey:SinaAppKey appSecret:SinaAppSecret redirectUri:SinaRedirectUri weiboSDKCls:[WeiboSDK class]]; #if TARGET_IPHONE_SIMULATOR#else //QQ好友 [ShareSDK connectQQWithQZoneAppKey:QZoneAppKey qqApiInterfaceCls:[QQApiInterface class] tencentOAuthCls:[TencentOAuth class]];#endif //微信朋友圈 [ShareSDK connectWeChatSessionWithAppId:WeiXinAppID wechatCls:[WXApi class]]; //微信好友 [ShareSDK connectWeChatTimelineWithAppId:WeiXinAppID wechatCls:[WXApi class]]; }); return [self adean_application:application didFinishLaunchingWithOptions:launchOptions];}- (BOOL)adean_application:(UIApplication *)application handleOpenURL:(NSURL *)url{ [ShareSDK handleOpenURL:url wxDelegate:self]; return [self adean_application:application handleOpenURL:url];}- (BOOL)adean_application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation{ [ShareSDK handleOpenURL:url sourceApplication:sourceApplication annotation:annotation wxDelegate:self]; return [self adean_application:application openURL:url sourceApplication:sourceApplication annotation:annotation];}- (void)adean_applicationDidReceiveMemoryWarning:(UIApplication *)application { [self adean_applicationDidReceiveMemoryWarning:application];}@end |
这下再去看下AppDelegate文件，代码不超过200行了。
小结
Method Swizzling常见的应用场景：
1.用于记录或者存储，比方说记录ViewController进入次数、Btn的点击事件、ViewController的停留时间等等。 可以通过Runtime获取到具体ViewController、Btn信息，然后传给服务器。
2.添加需要而系统没提供的方法，比方说修改Statusbar颜色。
3.用于轻量化、模块化处理，如上面介绍的，代码轻量化处理。
Method Swizzling是把双刃剑，需要正确理解它的使用。
分类增加变量的使用场景：
1.过多继承时，可以通过分类减少继承层级，清晰流程框架。比方说，ViewController可能需要相互冲突的事件，单一父类会导致逻辑复杂。这时候可以通过分类简化逻辑，不同的ViewController引用不同的分类。
2.扩展类属性。
上面我们学习了一些瘦身的技巧，希望通过这些方法写出更可读性更高，可维护性更高的代码。
提醒：
本文涉及到的Demo已经放到GitHub上了。Demo可能与本文有点出入，部分函数命名跟文章中不一致。