iOS热更新绕过了苹果的审核，之前有些开发者收到了警告邮件，最新通知显示如果App中包含热更新不作调整，有可能下架.JSPatch最开始用于修复严重的线上bug，后来发展为修改创建各种模块，导致偏离了最开始的初衷.

JSPatch

JSPatch源码在GitHub上面托管，可以直接拖入工程中，也可以通过CocoaPods导入：

pod 'JSPatch'

假设项目中某个按钮点击之后执行代码过程中发生了数组越界:

@interface ViewController ()

@property (strong, nonatomic) NSMutableArray *data;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.data = [[NSMutableArray alloc] init];
    [self.data addObject:@"FlyElephant"];
    [self.data addObject:@"Keso"];
    [self.data addObject:@"北京"];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)testAction:(UIButton *)sender {
    NSInteger index = 10;
    NSString *name = self.data[index];
    NSLog(@"数组%@",name);
}

@end

如果这个场景发生在生产环境中，开发人员要么重新打包上线，要么对天祈祷，JSPatch提供了第三种可能性，方法替换:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    [JPEngine startEngine];
    NSString *sourcePath = [[NSBundle mainBundle] pathForResource:@"main" ofType:@"js"];
    NSString *script = [NSString stringWithContentsOfFile:sourcePath encoding:NSUTF8StringEncoding error:nil];
    [JPEngine evaluateScript:script];
    
    return YES;
}

main.js中替换方法的代码:

require("NSMutableArray");

defineClass("ViewController", {
            testAction: function(sender) {
            var index = 0;
            var tempData = self.data().toJS();
            if (index >= 0 && index < tempData.length) {
            var name = tempData[index];
            console.log("数组:"+name);
            } else {
            console.log("索引数据不存在")
            }
            }
            }, {});

实现起来比较简单，这个实现我们只能实现本地替换，为了做到线上环境实时动态替换，就需要了解JSPatch热更新平台.

JSPatch 服务平台

Github 开源的是 JSPatch 核心代码，使用完全免费自由，若打算自己搭建后台下发 JSPatch 脚本，可以直接使用 github 上的核心代码，与 JSPatch 平台上的 SDK 无关。JSPatch 平台的 SDK 在核心代码的基础上增加了向平台请求脚本/传输解密/版本管理等功能，只用于这个平台。

如果公司体量足够完成有实力自己实现JSPatch的后台，定制自己需要的功能，出于学习目的可以注册JSPatch服务平台的账号.

按照官方指导文档，新建App

FlyElephant.png

生成公钥和私钥，mac终端执行openssl，执行以下命令:

openssl >
genrsa -out rsa_private_key.pem 1024
pkcs8 -topk8 -inform PEM -in rsa_private_key.pem -outform PEM –nocrypt
rsa -in rsa_private_key.pem -pubout -out rsa_public_key.pem

上传修复Bug的JS文件和私钥:

FlyElephant.png

App启动设置:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    [JSPatch startWithAppKey:@"AppKey"];
    [JSPatch setupRSAPublicKey:@"-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDN5NdQktnZ1pL8P1IXV2vJ8x+G\nSGORWCwjjUfnUwZD/bJust7JGvTXE/rt/AlnEFm\nR5U7d+7HEjI3gS14tR3ZGG/li83wmIvnMxGXfjwWQbN+EKoR7IGG6LDilqC+qDM3\nLPSwr2zkJtgsf4L2JQIDAQAB\n-----END PUBLIC KEY-----"];
    [JSPatch sync];
    return YES;
}

如果希望及时修复可DidBecomeActive唤醒App的时候同步JSPatch补丁:

- (void)applicationDidBecomeActive:(UIApplication *)application {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    [JSPatch sync];
}

测试代码:

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.data = [[NSMutableArray alloc] init];
    [self.data addObject:@"FlyElephant"];
    [self.data addObject:@"Keso"];
    [self.data addObject:@"北京"];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)testAction:(UIButton *)sender {
    NSInteger index = 10;
    NSString *name = self.data[index];
    NSLog(@"数组%@",name);
}

@end

同步更新热修复文件在Librayw文件夹下面:

Snip20170602_5.png

Swift

Swift实现方法交换需要在方法前面加入dynamic，同时需要类集成NSObject.
定义User类:

open class User:NSObject {
    
    dynamic func buyCourse() {
        print("FlyElephant---通过Swift购买图书")
    }
}

购买事件:

   @IBAction func buyAction(_ sender: UIButton) {
        
        let user:User = User()
        
        user.buyCourse()
    }

main.js 设置:

defineClass('FESwiftDemo.User', {
            buyCourse: function() {
            console.log('FlyElephant---通过JS购买课程')
            }
            })

App 启动设置:

   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        
        let path = Bundle.main.path(forResource: "main", ofType: "js")
        do {
            let patch = try String(contentsOfFile: path!)
            
            JPEngine.start()
            JPEngine.evaluateScript(patch)
            
        } catch {}
        return true
    }

参考链接:
JSPatch源码
JSPatch服务平台
Swift方法交换