iOS-无侵入的埋点方案

作者: 海文_L | 来源:发表于2020-08-26 16:19 被阅读0次

前言

埋点统计在产品运营过程中对用户行为分析、产品前期的业务模式探索起着很重要的作用。常用的三种埋点方式主要包括手动埋点、可视化埋点和无痕埋点。

手动埋点主要是通过手写代码的方式哪里需要埋哪里，优点是数据精准、方便调试、能够自定义所需的变量值，缺点是工作量较大、埋点代码多容易产生冗余、后期难维护等；
可视化埋点指前端或者APP端基于DOM元素和控件所精准自动埋点的上报的方案，优点是相比较于无埋点相而言对较低，但是这个可视化元素的识别技术是客户端或者前端所要实现的，唯一 ID 生成也无需客户端去自定义规则，这套生成规则由相关产品在自动化工具的情况下生成配置表，下发到客户端，再由客户端按坑就班到相关界面去实现、数据量相对精确。缺点是可视化工具的平台的搭建，静态页面的元素识别都需要额外开发、动态效果可能会遗漏。（可参考：可视化埋点(2)：iOS端实现）
无痕埋点指的是通过编译工具、预编译替换代码等，直接由SDK全部负责采集上报，优点是代码不会出现在业务代码中、容易管理和维护，缺点是后期的结息比较复杂、view_path不能做到100%唯一、后端或产品人员数据分析工作量大。

三种埋点方案中，可视化埋点和无痕埋点，都属于无侵入的埋点方案，因为它们都不需要在业务代码中写入埋点代码。采用无侵入埋点方案，既可以做到埋点被统一维护，又可以实现和工程代码的解耦。其中无痕埋点方案能够满足大多数应用的埋点需求。

无痕埋点方案介绍

最常见的三种埋点类型有页面进入次数、页面停留时间、点击事件。对于这三种常见的情况，我们都可以通过runtime的method swizzling来插入埋点代码，以实现无侵入的埋点方法，可分三步来处理：实现替换、生成唯一标识、数据上报。

新建一个方法替换类NSObject+Logger，加上替换的方法swizzleSelectorFromSelector : toSelector :，代码如下：

+ (void)swizzleSelectorFromSelector:(SEL)originalSelector toSelector:(SEL)swizzledSelector {
   Method originalMethod = class_getInstanceMethod(self, originalSelector);
   Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector);

   BOOL didAddMethod =
   class_addMethod(self,
                   originalSelector,
                   method_getImplementation(swizzledMethod),
                   method_getTypeEncoding(swizzledMethod));

   if (didAddMethod) {
       class_replaceMethod(self,
                           swizzledSelector,
                           method_getImplementation(originalMethod),
                           method_getTypeEncoding(originalMethod));
  } else {
       method_exchangeImplementations(originalMethod, swizzledMethod);
  }
}

这个方法利用运行时method_exchangeImplementations接口将方法的实现进行了交换，原方法调用时就会被hook住，从而去执行指定的方法。

页面进入次数、页面停留时间事件

页面进入次数、页面停留时间需要对UIViewController生命周期进行埋点，可以创建一个UIViewController的Category，通过NSObject+Logger将原生方法替换，代码如下：

+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
      Class class = NSClassFromString(@"UIViewController");
      [class swizzleSelectorFromSelector:@selector(viewWillAppear:) toSelector:@selector(hook_viewWillAppear:)];
      [class swizzleSelectorFromSelector:@selector(viewWillDisappear:) toSelector:@selector(hook_viewWillDisappear:)];
  });
}

- (void)hook_viewWillAppear:(BOOL)animated {
  //先执行插入代码，再执行原 viewWillAppear 方法
  [self insertToViewWillAppear];

  [self hook_viewWillAppear:animated];
}

- (void)hook_viewWillDisappear:(BOOL)animated {
  //先执行插入代码，再执行原 viewWillDisappear 方法
  [self insertToViewWillDisappear];

  [self hook_viewWillDisappear:animated];
}</pre>

数据上报部分这里没有做具体介绍，可以自行对接自己的后端接口或者一些第三方平台，如友盟。

## 点击事件

常用的控件如UIButton、UITextField、UISwitch、UISegmentedControl、UISlider 等，它们的父类都是UIControl ，我们可对sendAction:to:forEvent: 进行拦截，代码如下：

<pre spellcheck="false" class="md-fences md-end-block contain-cm modeLoaded" lang="" contenteditable="false" cid="n36" mdtype="fences" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none; box-sizing: border-box; overflow: visible; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 0.9em; white-space: normal; display: block; break-inside: avoid; text-align: left; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); border: 1px solid rgb(223, 226, 229); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; position: relative !important;">+ (void) load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
      //可监听到UIButton、UITextField、UISwitch、UISegmentedControl、UISlider 、UIStepper等控件的Action事件
      [self swizzleSelectorFromSelector:@selector(sendAction:to:forEvent:) toSelector:@selector(hook_sendAction:to:forEvent:)];
  });
}

#pragma mark--
#pragma 按钮点击
- (void)hook_sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
  [self insertToSendAction:action to:target forEvent:event];

  [self hook_sendAction:action to:target forEvent:event];
}

- (void)insertToSendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
  //日志记录
  if ([[[event allTouches] anyObject] phase] == UITouchPhaseEnded) {
      NSString *actionString = NSStringFromSelector(action);
      NSString *targetString = NSStringFromClass([target class]);

      NSLog(@"唯一标识：%@_%@_%@", targetString, self.accessibilityIdentifier, actionString);
  }
}

唯一标识

这里的唯一标识组成规则是NSStringFromClass([target class])+self.accessibilityIdentifier，accessibilityIdentifier+NSStringFromSelector(action)，accessibilityIdentifier系统默认为nil，我们需要根据不同控件的特性为accessibilityIdentifier进行赋值，如UIButton控件的accessibilityIdentifier可以是控件的变量名，考虑到用XIB或SB布局不一定会定义变量，可取button的title值或者image的名字来定义，新建一个UIView+Logger类：

@implementation UIView (Logger)

+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{        
      Class class = NSClassFromString(@"UIView");
      [class swizzleSelectorFromSelector:@selector(accessibilityIdentifier) toSelector:@selector(hook_accessibilityIdentifier)];
  });
}

#pragma mark - Method Swizzling
- (NSString *)hook_accessibilityIdentifier {
  NSString *labelStr = [self.superview findNameWithInstance:self];

  if (labelStr && ![labelStr isEqualToString:@""]) {
      //SB或XIB布局的，因获取不到image的name，所以至少要拉个变量名
      labelStr = [NSString stringWithFormat:@"%@",labelStr];
  } else {
      if ([self isKindOfClass:[UIButton class]]) {
          //UIButton 使用 button 的 text 和 image
          labelStr = [NSString stringWithFormat:@"%@%@",((UIButton *)self).titleLabel.text?:@"",((UIButton *)self).imageView.image.accessibilityIdentifier?:@""];
      }
  }

  [self setAccessibilityIdentifier:labelStr];
  return labelStr;
}

@end

findNameWithInstance:的实现

- (NSString *)findNameWithInstance:(UIView *)instance
{
  id nextResponder = [self nextResponder];
  NSString *name = [RuntimeHelper nameWithClass:self instance:instance];
  if (!name) {
      return [nextResponder findNameWithInstance:instance];
  }

  if ([name hasPrefix:@"_"]) { //去掉变量名的下划线前缀
      name = [name substringFromIndex:1];
  }

  return name;
}

这里又延伸出了一个问题，UIImage 并没有提供获取资源名字的方法。解决问题的方式是通过替换 UIImage 的 imageNamed: 方法对 UIImage的accessibilityIdentifier 进行赋值：

@implementation UIImage (Logger)
+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{        
      Class imageClass = NSClassFromString(@"UIImage");
      [object_getClass(imageClass) swizzleSelectorFromSelector:@selector(imageNamed:) toSelector:@selector(hook_imageNamed:)];
  });
}

+ (UIImage *)hook_imageNamed:(NSString *)imageName {
  UIImage *image = [UIImage hook_imageNamed:imageName];
  image.accessibilityIdentifier = imageName;
  return image;
}

Delegate事件

Delegate 事件的 swizzling 需要分成两步，第一步先替换掉 setDelegate: ，其次是对 Delegate 事件的替换，举个 UIScrollView 的例子：

//我们要保证在每个控制器里都执行一次，所以替换的方法都会加上class name的前缀，以示区别
#define GET_CLASS_CUSTOM_SEL(sel,class) NSSelectorFromString([NSString stringWithFormat:@"%@_%@",NSStringFromClass(class),NSStringFromSelector(sel)])

@implementation UIScrollView (Logger)
+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
      [[self class] swizzleSelectorFromSelector:@selector(setDelegate:) toSelector:@selector(hook_setDelegate:)];
  });
}

- (void)hook_setDelegate:(id<UIScrollViewDelegate>)delegate {
  // 由于setDelegate方法可能被多次调用，所以要判断是否已经swizzling了，防止重复执行。
  if (![[self class] delegate:delegate isContain:@selector(scrollViewWillBeginDragging:)]) {
      [self hook_scrollViewWillBeginDragging:delegate];
  }

  if ([NSStringFromClass([self class]) isEqualToString:@"UITableView"]){
      if (![[self class] delegate:delegate isContain:@selector(tableView:didSelectRowAtIndexPath:)]) {
          [(UITableView *)self hook_tableViewDidSelectRowAtIndexPathInClass:delegate];
      }
  }
  [self hook_setDelegate:delegate];
}

#pragma --
#pragma UIScrollViewDelegate
- (void)hook_scrollViewWillBeginDragging:(id<UIScrollViewDelegate>)delegate {
  [[self class] swizzleDelegate:delegate originSelector:@selector(scrollViewWillBeginDragging:) swizzleSelector:@selector(insertToScrollViewWillBeginDragging:)];
}

- (void)insertToScrollViewWillBeginDragging:(UIScrollView *)scrollView {
  SEL sel = GET_CLASS_CUSTOM_SEL(@selector(scrollViewWillBeginDragging:),[self class]);
  if ([self respondsToSelector:sel]) {
      IMP imp = [self methodForSelector:sel];
      void (*func)(id, SEL,id) = (void *)imp;

      NSLog(@"标识：%@_%@_%@", NSStringFromClass([self class]), [RuntimeHelper nameWithClass:self instance:scrollView], NSStringFromSelector(@selector(scrollViewWillBeginDragging:)));

      func(self, sel, scrollView);
  }
}

NSObject+Logger类新增 delegate: isContain:和 swizzleDelegate: originSelector: swizzleSelector:两个方法，完整代码如下：

#define GET_CLASS_CUSTOM_SEL(sel,class) NSSelectorFromString([NSString stringWithFormat:@"%@_%@",NSStringFromClass(class),NSStringFromSelector(sel)])

@implementation NSObject (Logger)
+ (void)swizzleSelectorFromSelector:(SEL)originalSelector toSelector:(SEL)swizzledSelector {
  Method originalMethod = class_getInstanceMethod(self, originalSelector);
  Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector);

//   NSLog(@"__delegateObject %@", [self class]);

  BOOL didAddMethod =
  class_addMethod(self,
                  originalSelector,
                  method_getImplementation(swizzledMethod),
                  method_getTypeEncoding(swizzledMethod));

  if (didAddMethod) {
      class_replaceMethod(self,
                          swizzledSelector,
                          method_getImplementation(originalMethod),
                          method_getTypeEncoding(originalMethod));
  } else {
      method_exchangeImplementations(originalMethod, swizzledMethod);
  }
}

+ (BOOL)delegate:(id)delegateObject isContain:(SEL)selector {
  return [self isContainSel:GET_CLASS_CUSTOM_SEL(selector, [delegateObject class]) inClass:[delegateObject class]];
}

+ (void)swizzleDelegate:(id)delegateObject originSelector:(SEL)originSelector swizzleSelector:(SEL)swizzleSelector {
  SEL newSelector = GET_CLASS_CUSTOM_SEL(originSelector, [delegateObject class]);
  Method swizzledMethod = class_getInstanceMethod([delegateObject class], swizzleSelector);

  //增加swizzle delegate method
  class_addMethod([delegateObject class],
                  newSelector,
                  method_getImplementation(class_getInstanceMethod([self class], swizzleSelector)),
                  method_getTypeEncoding(swizzledMethod));

  Method swizzleDelegateMethod = class_getInstanceMethod([delegateObject class], newSelector);
  Method originDelegateMethod = class_getInstanceMethod([delegateObject class], originSelector);

  // 将swizzle delegate method 和 origin delegate method 交换
  method_exchangeImplementations(swizzleDelegateMethod, originDelegateMethod);
}

+ (BOOL)isContainSel:(SEL)sel inClass:(Class)class {
  unsigned int count;

  Method *methodList = class_copyMethodList(class,&count);
  for (int i = 0; i < count; i++) {
      Method method = methodList[i];
      NSString *tempMethodString = [NSString stringWithUTF8String:sel_getName(method_getName(method))];
      if ([tempMethodString isEqualToString:NSStringFromSelector(sel)]) {
          return YES;
      }
  }
  return NO;
}

数据上报的方式这里没有做过多的介绍，可通过集成第三方统计平台或自搭服务进行对接，完整的DEMO参考这里。

参考文献：

可视化埋点(1)：思路

iOS无埋点数据统计实践

iOS-无侵入的埋点方案

前言

无痕埋点方案介绍

页面进入次数、页面停留时间事件

唯一标识

Delegate事件

参考文献：

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