Demo：https://github.com/cjckkk/PPpatch (by myself)
輕量級(jí)低風(fēng)險(xiǎn) iOS Hotfix 方案
我們都知道蘋(píng)果對(duì) Hotfix 抓得比較嚴(yán)，強(qiáng)大好用的 JSPatch 也成為了過(guò)去式。但即使測(cè)試地再細(xì)致，也難保線上 App 不出問(wèn)題，小問(wèn)題還能忍忍，大問(wèn)題就得重新走發(fā)布流程，然后等待審核通過(guò)，等待用戶(hù)升級(jí)，周期長(zhǎng)且麻煩。如果有一種方式相對(duì)比較安全，不需要 JSPatch 那么完善，但也足夠應(yīng)付一般場(chǎng)景，使用起來(lái)還比較輕量就好了，這也是本文要探討的主題。
要達(dá)到這個(gè)目的，Native 層只要透出兩種能力就基本可以了：
- 在任意方法前后注入代碼的能力，可能的話最好還能替換掉。
- 調(diào)用任意類(lèi)/實(shí)例方法的能力。
第 2 點(diǎn)不難，只要把 [NSObject performSelector:...] 那一套通過(guò) JSContext 暴露出來(lái)即可。難的是第 1 點(diǎn)。其實(shí)細(xì)想一下，這不就是 AOP 么，而 iOS 有一個(gè)很方便的 AOP Library: Aspects，只要把它的幾個(gè)方法通過(guò) JSContext 暴露給 JS 不就可以了么？
選擇 Aspects 的原因是它已經(jīng)經(jīng)過(guò)了驗(yàn)證，不光是功能上的，更重要的是可以通過(guò) AppStore 的審核。
This is stable and used in hundreds of apps since it’s part of PSPDFKit, an iOS PDF framework that ships with apps like Dropbox or Evernote.
Aspects 使用姿勢(shì)：
[UIViewController aspect_hookSelector:@selector(viewWillAppear:) withOptions:AspectPositionAfter usingBlock:^(id<AspectInfo> aspectInfo, BOOL animated) {
NSLog(@"View Controller %@ will appear animated: %tu", aspectInfo.instance, animated);
} error:NULL];
前插、后插、替換某個(gè)方法都可以。使用類(lèi)的方式很簡(jiǎn)單，NSClassFromString 即可，Selector 也一樣 NSSelectorFromString，這樣就能通過(guò)外部傳入 String，內(nèi)部動(dòng)態(tài)構(gòu)造 Class 和 Selector 來(lái)達(dá)到 Fix 的效果了。
這種方式的安全性在于：
- 不需要中間 JS 文件，準(zhǔn)備工作全部在 Native 端完成。
- 沒(méi)有使用 App Store 不友好的類(lèi)/方法。
Demo
假設(shè)線上運(yùn)行這這樣一個(gè) Class，由于疏忽，沒(méi)有對(duì)參數(shù)做檢查，導(dǎo)致特定情況下會(huì) Crash。
@interface MightyCrash: NSObject
- (float)divideUsingDenominator:(NSInteger)denominator;
@end
@implementation MightyCrash
// 傳一個(gè) 0 就 gg 了
- (float)divideUsingDenominator:(NSInteger)denominator
{
return 1.f/denominator;
}
@end
現(xiàn)在我們要避免 Crash，就可以通過(guò)這種方式來(lái)修復(fù)
[Felix fixIt];
NSString *fixScriptString = @" \
fixInstanceMethodReplace('MightyCrash', 'divideUsingDenominator:', function(instance, originInvocation, originArguments){ \
if (originArguments[0] == 0) { \
console.log('zero goes here'); \
} else { \
runInvocation(originInvocation); \
} \
}); \
\
";
[Felix evalString:fixScriptString];
運(yùn)行一下看看
MightyCrash *mc = [[MightyCrash alloc] init];
float result = [mc divideUsingDenominator:3];
NSLog(@"result: %.3f", result);
result = [mc divideUsingDenominator:0];
NSLog(@"won't crash");
// output
// result: 0.333
// Javascript log: zero goes here
// won't crash
It Works, 是不是有那么點(diǎn)意思了。以下是可以正常運(yùn)行的代碼，僅供參考。
#import <Aspects.h>
#import <objc/runtime.h>
#import <JavaScriptCore/JavaScriptCore.h>
@interface Felix: NSObject
+ (void)fixIt;
+ (void)evalString:(NSString *)javascriptString;
@end
@implementation Felix
+ (Felix *)sharedInstance
{
static Felix *sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
+ (void)evalString:(NSString *)javascriptString
{
[[self context] evaluateScript:javascriptString];
}
+ (JSContext *)context
{
static JSContext *_context;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_context = [[JSContext alloc] init];
[_context setExceptionHandler:^(JSContext *context, JSValue *value) {
NSLog(@"Oops: %@", value);
}];
});
return _context;
}
+ (void)_fixWithMethod:(BOOL)isClassMethod aspectionOptions:(AspectOptions)option instanceName:(NSString *)instanceName selectorName:(NSString *)selectorName fixImpl:(JSValue *)fixImpl {
Class klass = NSClassFromString(instanceName);
if (isClassMethod) {
klass = object_getClass(klass);
}
SEL sel = NSSelectorFromString(selectorName);
[klass aspect_hookSelector:sel withOptions:option usingBlock:^(id<AspectInfo> aspectInfo){
[fixImpl callWithArguments:@[aspectInfo.instance, aspectInfo.originalInvocation, aspectInfo.arguments]];
} error:nil];
}
+ (id)_runClassWithClassName:(NSString *)className selector:(NSString *)selector obj1:(id)obj1 obj2:(id)obj2 {
Class klass = NSClassFromString(className);
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
return [klass performSelector:NSSelectorFromString(selector) withObject:obj1 withObject:obj2];
#pragma clang diagnostic pop
}
+ (id)_runInstanceWithInstance:(id)instance selector:(NSString *)selector obj1:(id)obj1 obj2:(id)obj2 {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
return [instance performSelector:NSSelectorFromString(selector) withObject:obj1 withObject:obj2];
#pragma clang diagnostic pop
}
+ (void)fixIt
{
[self context][@"fixInstanceMethodBefore"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:NO aspectionOptions:AspectPositionBefore instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"fixInstanceMethodReplace"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:NO aspectionOptions:AspectPositionInstead instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"fixInstanceMethodAfter"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:NO aspectionOptions:AspectPositionAfter instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"fixClassMethodBefore"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:YES aspectionOptions:AspectPositionBefore instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"fixClassMethodReplace"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:YES aspectionOptions:AspectPositionInstead instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"fixClassMethodAfter"] = ^(NSString *instanceName, NSString *selectorName, JSValue *fixImpl) {
[self _fixWithMethod:YES aspectionOptions:AspectPositionAfter instanceName:instanceName selectorName:selectorName fixImpl:fixImpl];
};
[self context][@"runClassWithNoParamter"] = ^id(NSString *className, NSString *selectorName) {
return [self _runClassWithClassName:className selector:selectorName obj1:nil obj2:nil];
};
[self context][@"runClassWith1Paramter"] = ^id(NSString *className, NSString *selectorName, id obj1) {
return [self _runClassWithClassName:className selector:selectorName obj1:obj1 obj2:nil];
};
[self context][@"runClassWith2Paramters"] = ^id(NSString *className, NSString *selectorName, id obj1, id obj2) {
return [self _runClassWithClassName:className selector:selectorName obj1:obj1 obj2:obj2];
};
[self context][@"runVoidClassWithNoParamter"] = ^(NSString *className, NSString *selectorName) {
[self _runClassWithClassName:className selector:selectorName obj1:nil obj2:nil];
};
[self context][@"runVoidClassWith1Paramter"] = ^(NSString *className, NSString *selectorName, id obj1) {
[self _runClassWithClassName:className selector:selectorName obj1:obj1 obj2:nil];
};
[self context][@"runVoidClassWith2Paramters"] = ^(NSString *className, NSString *selectorName, id obj1, id obj2) {
[self _runClassWithClassName:className selector:selectorName obj1:obj1 obj2:obj2];
};
[self context][@"runInstanceWithNoParamter"] = ^id(id instance, NSString *selectorName) {
return [self _runInstanceWithInstance:instance selector:selectorName obj1:nil obj2:nil];
};
[self context][@"runInstanceWith1Paramter"] = ^id(id instance, NSString *selectorName, id obj1) {
return [self _runInstanceWithInstance:instance selector:selectorName obj1:obj1 obj2:nil];
};
[self context][@"runInstanceWith2Paramters"] = ^id(id instance, NSString *selectorName, id obj1, id obj2) {
return [self _runInstanceWithInstance:instance selector:selectorName obj1:obj1 obj2:obj2];
};
[self context][@"runVoidInstanceWithNoParamter"] = ^(id instance, NSString *selectorName) {
[self _runInstanceWithInstance:instance selector:selectorName obj1:nil obj2:nil];
};
[self context][@"runVoidInstanceWith1Paramter"] = ^(id instance, NSString *selectorName, id obj1) {
[self _runInstanceWithInstance:instance selector:selectorName obj1:obj1 obj2:nil];
};
[self context][@"runVoidInstanceWith2Paramters"] = ^(id instance, NSString *selectorName, id obj1, id obj2) {
[self _runInstanceWithInstance:instance selector:selectorName obj1:obj1 obj2:obj2];
};
[self context][@"runInvocation"] = ^(NSInvocation *invocation) {
[invocation invoke];
};
// helper
[[self context] evaluateScript:@"var console = {}"];
[self context][@"console"][@"log"] = ^(id message) {
NSLog(@"Javascript log: %@",message);
};
}
@end
--EOF--
轉(zhuǎn)載
http://limboy.me/tech/2018/03/04/ios-lightweight-hotfix.html
