一、简介
一、所谓的aop编程（面向切面编程），其原理也就是在不更改正常的业务流程的前提下，通过生成一个动态代理类，从而实现对目标对象嵌入附加的操作。在ios中，想要实现相似的效果也很简单，利用OC的动态性，通过Method Swizzling 改变目标函数的selector所指向的实现，然后在新的实现中实现附加的操作，完成之后再货到原来的处理逻辑。
二、在一个类没有实现源码的情况下，如果你要改变一个类的实现方法，你可以选择重继承该类，然后重写方法，或者使用Category类别名暴力抢先的方式。但是这两种方式，都需要我们在使用的时候改变我们的编程方式，或者继承该类，或者需要引入Category。下面推出的一种方式，不需要我们修改我们编写逻辑的代码，就能实现函数的Hook功能，那就是RunTime中的Method Swizzling—交换方法的实现。
二、实现原理
在Object-C中每一个Method都是由一个SEL（方法名的散列值）和一个方法实现的指针（IMP）组成，他们在类实例化过程中SEL和IMP一一对应组成我们需要的完整的Method。
struct objc_method {
SEL _Nonnull method_name OBJC2_UNAVAILABLE;
char * _Nullable method_types OBJC2_UNAVAILABLE;
IMP _Nonnull method_imp OBJC2_UNAVAILABLE;
} OBJC2_UNAVAILABLE;如果我们不做任何处理，SEL和IMP都是一一对应的。如果我们使用Method Swizzling交换Method1和Method2的实现的时候，我们只需要在运行时把IMP2和IMP3的指向地址做个交换就可以了。其实我们调用的就是RunTime中的
/**
* Exchanges the implementations of two methods.
*
* @param m1 Method to exchange with second method.
* @param m2 Method to exchange with first method.
*
* @note This is an atomic version of the following:
* \code
* IMP imp1 = method_getImplementation(m1);
* IMP imp2 = method_getImplementation(m2);
* method_setImplementation(m1, imp2);
* method_setImplementation(m2, imp1);
* \endcode
*/
OBJC_EXPORT void
method_exchangeImplementations(Method _Nonnull m1, Method _Nonnull m2)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);第一个参数为：原始方法名。
第二个参数为：交换方法名。
四、页面埋点的实现
我们新建一个UIViewController的分类
#import <UIKit/UIKit.h>
#import <objc/runtime.h>
NS_ASSUME_NONNULL_BEGIN
@interface UIViewController (AOP)
@end
@interface UIControl (AOP)
@end
typedef void(^StopScrollBlock)(UIScrollView *scrollView);
@interface UIScrollView (AOP)
@property(nonatomic, copy) StopScrollBlock stopScrollBlock;
@end
NS_ASSUME_NONNULL_END#import "UIViewController+AOP.h"
@implementation UIViewController (AOP)
+ (void)load
{
Method originalMtd = class_getInstanceMethod([self class], @selector(viewDidAppear:));
Method swizzleMtd = class_getInstanceMethod([self class], @selector(aop_viewDidAppear:));
method_exchangeImplementations(originalMtd, swizzleMtd);
Method originalMtd1 = class_getInstanceMethod([self class], @selector(viewWillDisappear:));
Method swizzleMtd1 = class_getInstanceMethod([self class], @selector(aop_viewWillDisAppear:));
method_exchangeImplementations(originalMtd1, swizzleMtd1);
}
- (void)aop_viewDidAppear:(BOOL)animated
{
/**
MTA业务操作 记录日志，上传服务器，页面显示
*/
[self aop_viewDidAppear:animated];
}
- (void)aop_viewWillDisAppear:(BOOL)animated
{
/**
MTA业务操作 记录日志，上传服务器，页面消失
*/
#ifdef DEBUG
if ([self isContainScrollView]) {
/**
关闭滑动场景的卡顿监控,在相关页面进行如下代码的打点
*/
}
#endif
[self aop_viewWillDisAppear:animated];
}
-(BOOL)isContainScrollView{
for (id view in self.view.subviews) {
if ([view isMemberOfClass:[UIScrollView class]]) {//判断当前VC是否有UIScrollView及其子类
return YES;
}
}
return NO;
}
@end
@implementation UIControl (AOP)
+ (void)load {
Method originalMtd = class_getInstanceMethod([self class], @selector(sendAction:to:forEvent:));
Method swizzleMtd = class_getInstanceMethod([self class], @selector(aop_sendAction:to:forEvent:));
method_exchangeImplementations(originalMtd, swizzleMtd);
Method originalMtd2 = class_getInstanceMethod([self class], @selector(sendActionsForControlEvents:));
Method swizzleMtd2 = class_getInstanceMethod([self class], @selector(aop_sendActionsForControlEvents:));
method_exchangeImplementations(originalMtd2, swizzleMtd2);
}
- (void)aop_sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
if ([self isKindOfClass:[UIButton class]]){
/**
MTA次数统计,某按钮点击及频率次数日志
*/
}
[self aop_sendAction:action to:target forEvent:event];
}
// 时长统计
- (void)aop_sendActionsForControlEvents:(UIControlEvents)controlEvents {
if (controlEvents == UIControlEventTouchDown){
/**
MTA 处理按钮点击事件
*/
NSLog(@"aop_sendAction ============= 时长统计 =============处理按钮点击事件 ");
}else if (controlEvents == UIControlEventTouchUpInside || controlEvents == UIControlEventTouchUpOutside){
/**
处理按钮松开状态
*/
NSLog(@"aop_sendAction ============= 时长统计 =============处理按钮松开状态 ");
}
[self aop_sendActionsForControlEvents:controlEvents];
}
@end
@implementation UIScrollView (AOP)
#pragma mark - Setter And Getter
static const char p_stopScrollBlock = '\0';
- (StopScrollBlock)stopScrollBlock {
return objc_getAssociatedObject(self, &p_stopScrollBlock);
}
- (void)setStopScrollBlock:(StopScrollBlock)stopScrollBlock {
objc_setAssociatedObject(self, &p_stopScrollBlock, stopScrollBlock, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
/**load初始化方法 代理方法互换*/
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Method originalMethod = class_getInstanceMethod([UIScrollView class], @selector(setDelegate:));
Method replaceMethod = class_getInstanceMethod([UIScrollView class], @selector(hook_setDelegate:));
method_exchangeImplementations(originalMethod, replaceMethod);
});
}
/*
1、快速滚动，自然停止；
2、快速滚动，手指按压突然停止；
3、慢速上下滑动停止
*/
#pragma mark - scrollView 停止滚动监测
- (void)stopScroll:(UIScrollView *)scrollView {
if (self.stopScrollBlock) {
self.stopScrollBlock(scrollView);
}
#ifdef DEBUG
NSLog(@"scrollView停止滚动了，存储日志上报服务器，可作为结束滑动钩子函数");
#endif
}
#pragma mark - Hook UIScrollView setDelegate
- (void)hook_setDelegate:(id<UIScrollViewDelegate>)delegate {
[self hook_setDelegate:delegate];
if ([self isMemberOfClass:[UIScrollView class]]) {
//Hook (scrollViewDidEndDecelerating:) 方法
Hook_Method([delegate class], @selector(scrollViewDidEndDecelerating:), [self class], @selector(p_scrollViewDidEndDecelerating:), @selector(add_scrollViewDidEndDecelerating:));
//Hook (scrollViewDidEndDragging:willDecelerate:) 方法
Hook_Method([delegate class], @selector(scrollViewDidEndDragging:willDecelerate:), [self class], @selector(p_scrollViewDidEndDragging:willDecelerate:), @selector(add_scrollViewDidEndDragging:willDecelerate:));
//Hook (scrollViewWillBeginDragging:) 方法
Hook_Method([delegate class], @selector(scrollViewWillBeginDragging:), [self class], @selector(p_scrollViewWillBeginDragging:), @selector(add_scrollViewWillBeginDragging:));
}
//不是UIScrollView，不需要hook方法
}
#pragma mark - Hook_Method //OC中static修饰方法有什么用？
static void Hook_Method(Class originalClass, SEL originalSel, Class replacedClass, SEL replacedSel, SEL noneSel){
//原实例方法
Method originalMethod = class_getInstanceMethod(originalClass, originalSel);
// 替换的实例方法
Method replacedMethod = class_getInstanceMethod(replacedClass, replacedSel);
// 如果没有实现 delegate 方法，则手动动态添加
if (!originalMethod) {
Method noneMethod = class_getInstanceMethod(replacedClass, noneSel);
BOOL addNoneMethod = class_addMethod(originalClass, originalSel, method_getImplementation(noneMethod), method_getTypeEncoding(noneMethod));
if (addNoneMethod) {
NSLog(@"******** 没有实现 (%@) 方法，手动添加成功！！",NSStringFromSelector(originalSel));
}
return;
}
// 向实现 delegate 的类中添加新的方法
// 这里是向 originalClass 的 replaceSel（@selector(p_scrollViewDidEndDecelerating:)） 添加 replaceMethod
BOOL addMethod = class_addMethod(originalClass, replacedSel, method_getImplementation(replacedMethod), method_getTypeEncoding(replacedMethod));
if (addMethod) {
//添加成功
NSLog(@"******** 实现了 (%@) 方法并成功 Hook 为 --> (%@)", NSStringFromSelector(originalSel), NSStringFromSelector(replacedSel));
// 重新拿到添加被添加的 method,这里是关键(注意这里 originalClass, 不 replacedClass), 因为替换的方法已经添加到原类中了, 应该交换原类中的两个方法
Method newMethod = class_getInstanceMethod(originalClass, replacedSel);
// 实现交换
method_exchangeImplementations(originalMethod, newMethod);
}else {
// 添加失败，则说明已经 hook 过该类的 delegate 方法，防止多次交换。
NSLog(@"******** 已替换过，避免多次替换 --> (%@)",NSStringFromClass(originalClass));
}
}
// 已经实现需要hook的代理方法时，调用此处方法进行替换
#pragma mark - Replace_Method
- (void)p_scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
[self p_scrollViewDidEndDecelerating:scrollView];
// 停止类型1、停止类型2
BOOL scrollToScrollStop = !scrollView.tracking && !scrollView.dragging && !scrollView.decelerating;
if (scrollToScrollStop) {
[scrollView stopScroll:scrollView];
}
}
- (void)p_scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
NSLog(@"%s", __func__);
[self p_scrollViewDidEndDragging:scrollView willDecelerate:decelerate];
if (!decelerate) {
// 停止类型3
BOOL dragToDragStop = scrollView.tracking && !scrollView.dragging && !scrollView.decelerating;
if (dragToDragStop) {
[scrollView stopScroll:scrollView];
}
}
}
- (void)p_scrollViewWillBeginDragging:(UIScrollView *)scrollView {
NSLog(@"%s", __func__);
[self p_scrollViewWillBeginDragging:scrollView];
#ifdef DEBUG
NSLog(@"开始监听到scrollView开始滑动,存储日志上报服务器");
#endif
}
// 那没有实现需要hook的代理方法时，调用此处方法
#pragma mark - Add_Method
- (void)add_scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
// 停止类型1、停止类型2
BOOL scrollToScrollStop = !scrollView.tracking && !scrollView.dragging && !scrollView.decelerating;
if (scrollToScrollStop) {
[scrollView stopScroll:scrollView];
}
}
- (void)add_scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
NSLog(@"%s", __func__);
if (!decelerate) {
// 停止类型3
BOOL dragToDragStop = scrollView.tracking && !scrollView.dragging && !scrollView.decelerating;
if (dragToDragStop) {
[scrollView stopScroll:scrollView];
}
}
}
- (void)add_scrollViewWillBeginDragging:(UIScrollView *)scrollView {
NSLog(@"%s", __func__);
#ifdef DEBUG
NSLog(@"开始监听到scrollView开始滑动,存储日志上报服务器");
#endif
}
@end
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