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@xifenglang-33250 2017-01-07T00:50:42.000000Z 字数 11824 阅读 2200

Runtime Method Swizzling 实践小结

iOS_Runtime

  1. #import <objc/runtime.h>

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Method Swizzling 的实现

对于Runtime Swizzling,这篇文章值得一看：《Objective-C的方法替换》，俺目前只实现了对一个类的2个“方法”进行Method Swizzling,对不同的类进行Method Swizzling出现了奇怪的问题，已放弃研究。
Method Swizzling尽量少用，这是把利剑，用好了能省很多事，用不好就可能成为猪队友。

交换实例方法

  1. /**
  2.  【Method Swizzling-慎用】用于替换同一类的2个[实例]方法。建议放在+(void)load方法配合DispatchOnce一起使用
  4.  @param originalSEL 被替换的SEL
  5.  @param objectSEL   用于替换的自定义SEL
  6.  @param objectClass 进行Method Swizzling的Class
  7.  */
  8. void JK_ExchangeInstanceMethod(SEL originalSEL, SEL objectSEL, Class objectClass);
  12. void JK_ExchangeInstanceMethod(SEL originalSEL, SEL objectSEL, Class objectClass) {
  13.     Method originalMethod = class_getInstanceMethod(objectClass, originalSEL);
  14.     Method replaceMethod = class_getInstanceMethod(objectClass, objectSEL);
  16.     // 判断是否实现方法
  17.     if (originalMethod == NULL || replaceMethod == NULL) {
  18.         NSLog(@"\n.\tWarning! JK_ExchangeInstanceMethod 失败!  [%@及其SuperClasses] 均未实现方法 [%@]\n.",objectClass,originalMethod == NULL ? NSStringFromSelector(originalSEL) : NSStringFromSelector(objectSEL));
  19.         return;
  20.     }
  22.     // 将replaceMethod实现添加到objectClass中，并且将originalSEL指向新添加的replaceMethod的IMP。
  23.     BOOL add = class_addMethod(objectClass, originalSEL, method_getImplementation(replaceMethod), method_getTypeEncoding(replaceMethod));
  25.     if (add) {
  26.         // 添加成功，再将objectSEL指向原有的originalMethod的IMP，实现交换
  27.         // 当前类或者父类没有实现originalSEL会执行这一步
  28.         class_replaceMethod(objectClass, objectSEL, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
  30.     } else {
  31.         // 已经实现customMethod，对systemMethod和customMethod的实现指针IMP进行交换
  32.         method_exchangeImplementations(originalMethod, replaceMethod);
  33.     }
  34. }

用作测试的类继承关系如：ViewController -> BaseViewController -> UIViewController
用作测试的originalSEL：@selector(viewWillAppear:)
进行以下操作：

  1. 对ViewController进行ExchangeInstanceMethod，objectSEL：@selector(edf_viewWillAppear:)，而且ViewController和父类BaseViewController都【没有实现viewWillAppear】，
    add = YES;

  2. 对UIViewController基类进行ExchangeInstanceMethod，objectSEL：@selector(jk_viewWillAppear:)，
    add = NO。

  3. 在操作2的基础上，如果在任何手动创建的类.m的(+ load)方法中执行操作1【不实现viewWillAppear:】,
    add = YES，对于ViewController只会执行@selector(edf_viewWillAppear:),不会执行@selector(jk_viewWillAppear:),其他控制器则会执行@selector(jk_viewWillAppear:)。标记点1

  4. 在操作2的基础上，如果在任何手动创建的类.m除【(+ load)以外】的方法中执行操作1【不实现viewWillAppear:】,
    add = YES，对于ViewController既执行@selector(edf_viewWillAppear:)又执行@selector(jk_viewWillAppear:),其他控制器则会执行@selector(jk_viewWillAppear:)。

  5. 在操作2的基础上，如果在任何手动创建的类.m的(+ load)方法中执行操作1，但是ViewController或者父类BaseViewController正常【实现了viewWillAppear:方法】,
    add = NO，对于ViewController既执行@selector(edf_viewWillAppear:)又执行@selector(jk_viewWillAppear:),其他控制器则会执行@selector(jk_viewWillAppear:),和操作4结果差不多。

初步得出的结论是 当前类或者父类没有实现originalSEL时（UIViewController排除在外），add = YES，并且执行class_addMethod前后的class_getInstanceMethod(objectClass, originalSEL)的指针地址不一样。
add = NO的时候，class_addMethod前后的class_getInstanceMethod(objectClass, originalSEL)的指针地址一样。

个人对Swizzling结果的理解是对2个SEL所关联的2个IMP进行了调换。
交换前：调用SEL1，会执行IMP_1对应的代码

SEL1 ---> IMP_1
SEL2 ---> IMP_2

交换后：调用SEL2，会执行IMP_1对应的代码

SEL1 ---> IMP_2
SEL2 ---> IMP_1

建议进行Swizzling的objectClass是拥有originalSEL的最顶层父类，先从顶层父类开始选，比如UIViewController，而不是底层的子类，比如普通的控制器类。

交换类方法

  1. /**
  2.  【Method Swizzling-慎用】用于替换同一类的2个[类]方法。建议放在+(void)load方法使用
  4.  @param originalSEL 被替换的SEL
  5.  @param objectSEL   用于替换的自定义SEL
  6.  @param objectClass 进行Method Swizzling的Class
  7.  */
  8. void JK_ExchangeClassMethod(SEL originalSEL, SEL objectSEL, Class objectClass);
  12. void JK_ExchangeClassMethod(SEL originalSEL, SEL objectSEL, Class objectClass) {
  13.     Method originalMethod = class_getClassMethod(objectClass, originalSEL);
  14.     Method replaceMethod = class_getClassMethod(objectClass, objectSEL);
  17.     if (originalMethod == NULL || replaceMethod == NULL) {
  18.         NSLog(@"\n.\tWarning! JK_ExchangeClassMethod 失败!  [%@及其SuperClasses] 均未实现方法 [%@]\n.",objectClass,originalMethod == NULL ? NSStringFromSelector(originalSEL) : NSStringFromSelector(objectSEL));
  19.         return;
  20.     }
  22.     /// 交换实例方法的写法在这失效了，所以直接进行了method_exchangeImplementations，待研究
  23.     method_exchangeImplementations(originalMethod, replaceMethod);
  24. }

------------------------------------------------------

Method Swizzling 的应用

打印当前显示的控制器ViewController

  1. @implementation UIViewController (Swizzling)
  3. + (void)load {
  4. #ifdef DEBUG
  5.     static dispatch_once_t onceToken;
  6.     dispatch_once(&onceToken, ^{
  7.         JK_ExchangeInstanceMethod(@selector(viewWillAppear:), @selector(jk_viewWillAppear:), self);
  8.     });
  9. #endif
  10. }
  13. - (void)jk_viewWillAppear:(BOOL)animated{
  14.     [self jk_viewWillAppear:animated];
  16.     NSString * className = NSStringFromClass([self class]);
  17.     if (![className hasPrefix:@"UI"] && ![className hasPrefix:@"_"]) {
  18.         NSLog(@"即将显示:%@   备注:%@",self.class,self.view.accessibilityIdentifier);
  19.     }
  20. }
  22. @end

UIImage优先使用无缓存加载

加载UIImage有2种方式：

方式1会不断增加缓存，直到APP进程被杀才会释放，适用于频繁使用的图片，存放在Assets.xcassets中图片必须[UIImage imageNamed...]。
方式2不会被缓存，Image对象释放即可释放内存，适用于不怎么用的图片，而且存在于[NSBundle mainBundle]中，不能存放在Assets.xcassets中。

  1. @implementation UIImage (Swizzling)
  2. + (void)load{
  3.     static dispatch_once_t onceToken;
  4.     dispatch_once(&onceToken, ^{
  5.         JK_ExchangeClassMethod(@selector(imageNamed:), @selector(jk_imageNamed:), self);
  6.     });
  7. }
  10. /**
  11.  优先无缓存加载图片,imageWithContentsOfFile
  12.  */
  13. + (UIImage *)jk_imageNamed:(NSString *)name{
  14.     UIImage * image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:name ofType:[name hasSuffix:@"jpg"] ? nil : @"png"]];
  15.     if (!image) {
  16.         image = [self jk_imageNamed:name];
  17.     }
  19.     if (image == nil) {
  20.         NSLog(@"\nWarning! 图片加载失败!  imageName:%@",name);
  21.     }
  22.     return image;
  23. }
  25. @end

打印字典NSDictionary中的中文

打印NSDictionary中的中文，针对网络请求到的数据

  1. @implementation NSDictionary (Swizzling)
  3. + (void)load {
  4. #ifdef DEBUG
  5.         static dispatch_once_t onceToken;
  6.         dispatch_once(&onceToken, ^{
  7.             JK_ExchangeInstanceMethod(@selector(descriptionWithLocale:), @selector(jk_descriptionWithLocale:), self);
  8.         });
  9. #endif
  10. }
  13. - (NSString *)jk_descriptionWithLocale:(id)locale {
  14.     if (self == nil || self.allKeys.count == 0) {
  15.         return [self jk_descriptionWithLocale:locale];
  16.     } else {
  17.         @try {
  18.             NSError * error = nil;
  19.             NSData * data = [NSJSONSerialization dataWithJSONObject:self options:NSJSONWritingPrettyPrinted error:&error];
  20.             if (error) {
  21.                 return [self jk_descriptionWithLocale:locale];
  22.             } else {
  23.                 return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  24.             }
  25.         } @catch (NSException *exception) {
  26.             return [self jk_descriptionWithLocale:locale];
  27.         }
  28.     }
  29. }
  31. @end

打印数组NSArray中的中文(按需使用)

打印NSArray中的中文，针对网络请求到的数据，一般Json都会用字典包裹，所以可以不用或者注释下面的代码，毕竟数组一般都是存Model，Json转换不了，加了@try之后发生异常时会被断点捕获。（正常情况下转换NSJSONSerialization不支持的类型，会直接Crash）

  1. @implementation NSArray (Swizzling)
  3. + (void)load {
  4. #ifdef DEBUG
  5.         static dispatch_once_t onceToken;
  6.         dispatch_once(&onceToken, ^{
  7.             JK_ExchangeInstanceMethod(@selector(descriptionWithLocale:), @selector(jk_descriptionWithLocale:), self);
  8.         });
  9. #endif
  10. }
  13. - (NSString *)jk_descriptionWithLocale:(id)locale {
  14.     if (self == nil || self.count == 0) {
  15.         return [self jk_descriptionWithLocale:locale];
  16.     } else {
  17.         @try {
  18.             NSError * error = nil;
  19.             NSData * data = [NSJSONSerialization dataWithJSONObject:self options:NSJSONWritingPrettyPrinted error:&error];
  20.             if (error) {
  21.                 return [self jk_descriptionWithLocale:locale];
  22.             } else {
  23.                 return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  24.             }
  25.         } @catch (NSException *exception) {
  26.             return [self jk_descriptionWithLocale:locale];
  27.         }
  28.     }
  29. }
  31. @end

防止NSMutableArray 插入nil、数组越界导致崩溃

慎用， 可能会变相的造成数据异常

  1. @implementation NSArray (SafeSwizzling)
  2. static const char * kArrayClass = "__NSArrayI";
  4. + (void)load {
  5.     static dispatch_once_t onceToken;
  6.     dispatch_once(&onceToken, ^{
  7.         JK_ExchangeInstanceMethod(@selector(objectAtIndex:), @selector(jk_objectAtIndexI:), objc_getClass(kArrayClass));
  8.     });
  9. }
  11. - (id)jk_objectAtIndexI:(NSUInteger)index {
  12.     if (index < self.count) {
  13.         return [self jk_objectAtIndexI:index];
  14.     } else {
  15.         NSLog(@"数组查询越界,return <null>。 --[NSArray objectAtIndex:]-- index=%zd   array.count=%zd",index,self.count);
  16.         return [NSNull null];
  17.     }
  18. }
  19. @end
  22. @implementation NSMutableArray (SafeSwizzling)
  23. static const char * kMutArrayClass = "__NSArrayM";
  25. + (void)load {
  26.     static dispatch_once_t onceToken;
  27.     dispatch_once(&onceToken, ^{
  28.         JK_ExchangeInstanceMethod(@selector(insertObject:atIndex:), @selector(jk_insertObject:atIndex:), objc_getClass(kMutArrayClass));
  29.         JK_ExchangeInstanceMethod(@selector(objectAtIndex:), @selector(jk_objectAtIndexM:), objc_getClass(kMutArrayClass));
  30.     });
  31. }
  33. - (void)jk_insertObject:(id)anObject atIndex:(NSUInteger)index {
  34.     if (index > self.count) {
  35.         NSLog(@"数组插值越界 --[NSMutableArray insertObject: atIndex:]-- object=%@   index=%zd      array.count=%zd",anObject,index,self.count);
  36.     } else if (anObject != nil) {
  37.         [self jk_insertObject:anObject atIndex:index];
  38.     } else {
  39.         NSLog(@"传入空值Nil --[NSMutableArray insertObject: atIndex:]-- object=%@   index=%zd",anObject,index);
  40.     }
  41. }
  43. - (id)jk_objectAtIndexM:(NSUInteger)index {
  44.     if (index < self.count) {
  45.         return [self jk_objectAtIndexM:index];
  46.     } else {
  47.         NSLog(@"数组查询越界,return <null>。 --[NSMutableArray objectAtIndex:]-- index=%zd   array.count=%zd",index,self.count);
  48.         return [NSNull null];
  49.     }
  50. }
  52. @end

防止MutableDictionary 传入nil导致崩溃

慎用，可能会变相的造成数据异常

  1. @implementation NSMutableDictionary (SafeSwizzling)
  2. static const char * kMutDictClass = "__NSDictionaryM";
  3. + (void)load {
  4.     static dispatch_once_t onceToken;
  5.     dispatch_once(&onceToken, ^{
  6.         JK_ExchangeInstanceMethod(@selector(setObject:forKey:), @selector(jk_setObject:forKey:), objc_getClass(kMutDictClass));
  7.     });
  8. }
  9. - (void)jk_setObject:(id)anObject forKey:(id<NSCopying>)aKey {
  10.     if (anObject && aKey) {
  11.         [self jk_setObject:anObject forKey:aKey];
  12.     } else {
  13.         NSLog(@"传入空值Nil --[NSMutableDictionary setObject: forKey:]-- object=%@   key=%@",anObject,aKey);
  14.     }
  15. }
  16. @end

拦截系统自带的导航栏'返回'按钮的Pop事件

参考了UIViewController-BackButtonHandler
分类.h

  1. /**
  2.  需要拦截导航栏上系统自带的‘返回’按钮事件，就实现此协议方法
  3.  */
  4. @protocol JKViewControllerPopActionHandler <NSObject>
  6. @optional
  7. - (BOOL)jk_navigationControllerShouldPopOnBackButton;
  9. @end
  12. /**
  13.  所有控制器都遵守JKViewControllerPopActionHandler协议
  14.  */
  15. @interface UIViewController (PopActionHandler)<JKViewControllerPopActionHandler>
  16. @end
  20. /**
  21.  用Runtime Method Swizzling拦截@selector(navigationBar:shouldPopItem:)
  22.  */
  23. @interface UINavigationController (PopActionHandler)
  24. @end

分类.m

  1. @implementation UIViewController (PopActionHandler)
  3. + (void)load {
  4.     static dispatch_once_t onceToken;
  5.     dispatch_once(&onceToken, ^{
  6.         JK_ExchangeInstanceMethod(@selector(viewDidAppear:), @selector(jk_viewDidAppear:), self);
  7.         JK_ExchangeInstanceMethod(@selector(viewDidDisappear:), @selector(jk_viewDidDisappear:), self);
  8.     });
  9. }
  12. - (void)jk_viewDidAppear:(BOOL)animated {
  13.     [self jk_viewDidAppear:animated];
  14.     if ([self respondsToSelector:@selector(jk_navigationControllerShouldPopOnBackButton)]) {
  15.         /// 拦截Pop事件就关闭侧滑返回
  16.         self.navigationController.interactivePopGestureRecognizer.enabled = NO;
  17.     }
  18. }
  20. - (void)jk_viewDidDisappear:(BOOL)animated {
  21.     [self jk_viewDidDisappear:animated];
  22.     self.navigationController.interactivePopGestureRecognizer.enabled = YES;
  23. }
  24. @end
  28. @implementation UINavigationController (PopActionHandler)
  30. + (void)load {
  31.     static dispatch_once_t onceToken;
  32.     dispatch_once(&onceToken, ^{
  33.         JK_ExchangeInstanceMethod(@selector(navigationBar:shouldPopItem:), @selector(jk_navigationBar:shouldPopItem:), self);
  34.     });
  35. }
  39. - (BOOL)jk_navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {
  40.     if([self.viewControllers count] < [navigationBar.items count]) {
  41.         return YES;
  42.     }
  43.     UIViewController* topVC = [self topViewController];
  44.     BOOL enablePop = YES;
  45.     if ([topVC respondsToSelector:@selector(jk_navigationControllerShouldPopOnBackButton)]) {
  46.         enablePop = [topVC jk_navigationControllerShouldPopOnBackButton];
  47.     }
  49.     if (enablePop == YES) {
  50.         dispatch_async(dispatch_get_main_queue(), ^{
  51.             [self popViewControllerAnimated:YES];
  52.         });
  53.     }
  54.     return NO;
  55. }
  58. @end

防止重复点击按钮Button、拦截某些系统自带按钮的点击事件

代码就不贴了,搜一下有一堆，随便推荐一篇文章iOS 解决button重复点击问题。
我的建议是有需要才做处理重复点击，创建的Button默认不处理重复点击，文章中是拦截处理了所有UIControl的点击事件，会对某些系统按钮也会拦截点，所以要对某些类做特殊处理，下面是我碰到过的。

  1. // 拍照的控制器
  2. if ([target isKindOfClass:NSClassFromString(@"PLImagePickerCameraView")]
  3.         // 网页视频播放器
  4.         || [target isKindOfClass:NSClassFromString(@"AVFullScreenPlaybackControlsViewController")]
  5.         // iOS10 拍照
  6.         || [target isKindOfClass:NSClassFromString(@"CAMViewfinderViewController")]
  7.         || [target isKindOfClass:[UIBarButtonItem class]]) {
  8.         // 系统拍照按钮/视频播放器按钮单独处理，其他需要快速点击的设置quickTapEnable = YES
  9.         [self jk_sendAction:action to:target forEvent:event];
  10.         return;
  11.     }

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