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简介
MLeaksFinder是微信开源的可以在iOS开发阶段用来检测内存泄漏的库，可以自动的在UIView和UIViewController中发现泄漏，通过弹出框显示在View-ViewController中的泄漏对象。除了发现UIView和UIViewController的泄漏对象，开发者也可以扩展到其他类型的对象。 并且可以通过FBRetainCycleDetector找到引用环。 内存分类 Leaked memory 不被应用引用的内存，无法再次使用或者释放（可以使用Leaks Instrument工具检测到） Abandoned memory 没有用处的，仍被应用引用的内存 Cached memory 仍然被应用引用，可以被再次使用从而得到更好的性能 原理除了单例及其持有它的强引用，当一个UIViewController被pop或dismiss后，对应的View，View的subViews等对象将很快被释放。 HookHook所有页面退出的情况作为检测时机 UIViewController -dismiss -viewDidDisappearUINavigationController -pop -popToRoot -popToViewController视图层级 从上述的页面生命周期可以看到，viewDidDisappear在页面做push的时候也会触发，所以不能单独以viewDidDisappear作为检测时机，需要以先有popViewControllerAnimated，后有viewDidDisappear为特征，才能作为页面出栈的判断。 Left-edge swipeUINavigationController -pop有一种特殊情况是左滑手势 先左滑-后松开 -[MyUINavigationController popViewControllerAnimated:] -[ChildViewController viewWillDisappear:] -[ParentViewController viewWillAppear:] -[ParentViewController viewWillDisappear:] -[ParentViewController viewDidDisappear:] -[ChildViewController viewWillAppear:] -[ChildViewController viewDidAppear:]先左滑-后完成 -[MyUINavigationController popViewControllerAnimated:] -[ChildViewController viewWillDisappear:] -[ParentViewController viewWillAppear:] -[ChildViewController viewDidDisappear:] -[ParentViewController viewDidAppear:] -[ChildViewController dealloc]由于左滑开始的时候，popViewControllerAnimated已经触发，而且时长由用户决定。由于检测需要使用延迟执行，查看页面等对象是否释放，所以不能单独以 popViewControllerAnimated为检测时机，需要以先有popViewControllerAnimated，后有viewDidDisappear为特征，才能作为页面出栈的判断。 popToRoot/popToViewController -[MyUINavigationController pushViewController:animated:] -[MyUINavigationController pushViewController:animated:] -[ParentViewController viewWillDisappear:] -[OtherViewController viewWillAppear:] -[ParentViewController viewDidDisappear:] -[OtherViewController viewDidAppear:] -[OtherViewController viewWillDisappear:] -[ChildViewController viewWillAppear:] -[OtherViewController viewDidDisappear:] -[ChildViewController viewDidAppear:] -[MyUINavigationController popToRootViewControllerAnimated:] -[ChildViewController viewWillDisappear:] -[ParentViewController viewWillAppear:] -[OtherViewController dealloc] -[ChildViewController viewDidDisappear:] -[ParentViewController viewDidAppear:] -[ChildViewController dealloc]从页面生命周期可以看到，除了TopViewController和RootViewController/ToViewController，其他处于中间的ViewController在弹出页面栈的时候不会有生命周期的调用，可以获取中间的ViewController开始检测。 UIViewController -present/dismiss ModalModal是指模态，模式状态，模态是人机交互过程中的一种状态，表现为用户相同的操作下可以产生不同的结果。例如使打开文件夹时，点击和右击会触发不同的效果。弹框也有对应的对话框，弹出框，全屏框等效果。 根据Modal的不同，ParentViewController的Appear状态会不同，当ParentViewController完全被遮挡的时候，会有Appear相关的页面生命周期变化。 不同模态下的页面生命周期不同，可以分为3类。 半覆盖 UIModalPresentationPageSheet UIModalPresentationFormSheet UIModalPresentationAutomatic UIModalPresentationCustom UIModalPresentationPopover -[ParentViewController presentViewController:animated:completion:] -[ChildViewController viewWillAppear:] -[ChildViewController viewDidAppear:] -[ChildViewController dismissViewControllerAnimated:completion:] -[ChildViewController viewWillDisappear:] -[ChildViewController viewDidDisappear:] -[ChildViewController dealloc] 全覆盖 UIModalPresentationCurrentContext UIModalPresentationFullScreen -[ParentViewController presentViewController:animated:completion:] -[ParentViewController viewWillDisappear:] -[ChildViewController viewWillAppear:] -[ChildViewController viewDidAppear:] -[ParentViewController viewDidDisappear:] -[ChildViewController dismissViewControllerAnimated:completion:] -[ChildViewController viewWillDisappear:] -[ParentViewController viewWillAppear:] -[ParentViewController viewDidAppear:] -[ChildViewController viewDidDisappear:] -[ChildViewController dealloc] 报错 UIModalPresentationOverFullScreen UIModalPresentationNone *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'The specified modal presentation style doesn't have a corresponding presentation controller.'这两种模态，会导致报OC语言层面异常，模态展示方式和对应controller不匹配 代码解析使用了Method Swizzle对页面的生命周期进行了Hook Method SwizzleNSObject (MemoryLeak)中对swizzle做了封装 + (void)swizzleSEL:(SEL)originalSEL withSEL:(SEL)swizzledSEL { #if _INTERNAL_MLF_ENABLED Class class = [self class]; Method originalMethod = class_getInstanceMethod(class, originalSEL); Method swizzledMethod = class_getInstanceMethod(class, swizzledSEL); BOOL didAddMethod = class_addMethod(class, originalSEL, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod)); if (didAddMethod) { class_replaceMethod(class, swizzledSEL, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod)); } else { method_exchangeImplementations(originalMethod, swizzledMethod); } #endif }使用宏作为功能开关，DEBUG的状态下打开，或者手动设置MEMORY_LEAKS_FINDER_ENABLED为1打开 //#define MEMORY_LEAKS_FINDER_ENABLED 0 #ifdef MEMORY_LEAKS_FINDER_ENABLED #define _INTERNAL_MLF_ENABLED MEMORY_LEAKS_FINDER_ENABLED #else #define _INTERNAL_MLF_ENABLED DEBUG #endif UINavigationController (MemoryLeak) popViewControllerAnimated在该生命周期中标记kHasBeenPoppedKey为YES - (UIViewController *)swizzled_popViewControllerAnimated:(BOOL)animated { UIViewController *poppedViewController = [self swizzled_popViewControllerAnimated:animated]; if (!poppedViewController) { return nil; } // Detail VC in UISplitViewController is not dealloced until another detail VC is shown if (self.splitViewController && self.splitViewController.viewControllers.firstObject == self && self.splitViewController == poppedViewController.splitViewController) { objc_setAssociatedObject(self, kPoppedDetailVCKey, poppedViewController, OBJC_ASSOCIATION_RETAIN); return poppedViewController; } // VC is not dealloced until disappear when popped using a left-edge swipe gesture extern const void *const kHasBeenPoppedKey; objc_setAssociatedObject(poppedViewController, kHasBeenPoppedKey, @(YES), OBJC_ASSOCIATION_RETAIN); return poppedViewController; }在UIViewController的viewWillAppear中，标记kHasBeenPoppedKey为NO - (void)swizzled_viewWillAppear:(BOOL)animated { [self swizzled_viewWillAppear:animated]; objc_setAssociatedObject(self, kHasBeenPoppedKey, @(NO), OBJC_ASSOCIATION_RETAIN); } popToViewController获取中间的ViewController开始检测 - (NSArray *)swizzled_popToViewController:(UIViewController *)viewController animated:(BOOL)animated { NSArray *poppedViewControllers = [self swizzled_popToViewController:viewController animated:animated]; for (UIViewController *viewController in poppedViewControllers) { [viewController willDealloc]; } return poppedViewControllers; } popToRootViewControllerAnimated获取中间的ViewController开始检测 - (NSArray *)swizzled_popToRootViewControllerAnimated:(BOOL)animated { NSArray *poppedViewControllers = [self swizzled_popToRootViewControllerAnimated:animated]; for (UIViewController *viewController in poppedViewControllers) { [viewController willDealloc]; } return poppedViewControllers; } UIViewController (MemoryLeak) viewDidDisappear判断kHasBeenPoppedKey为YES，然后开始检测 - (void)swizzled_viewDidDisappear:(BOOL)animated { [self swizzled_viewDidDisappear:animated]; if ([objc_getAssociatedObject(self, kHasBeenPoppedKey) boolValue]) { [self willDealloc]; } } dismissViewControllerAnimated - (void)swizzled_dismissViewControllerAnimated:(BOOL)flag completion:(void (^)(void))completion { [self swizzled_dismissViewControllerAnimated:flag completion:completion]; UIViewController *dismissedViewController = self.presentedViewController; if (!dismissedViewController && self.presentingViewController) { dismissedViewController = self; } if (!dismissedViewController) return; [dismissedViewController willDealloc]; }对应的presentedViewController，presentingViewController，self对应如下，获取到dismissedViewController并执行检测。由于dismissedViewController并没有边缘手势的影响，不需要使用dimiss和viewDidDisappear叠加的方式来判断检测的时机。 -[ChildViewController dismissViewControllerAnimated:completion:] self.presentedViewController (null) self.presentingViewController self -[ChildViewController viewWillDisappear:] -[ChildViewController viewDidDisappear:] -[ChildViewController dealloc] Action获取对应类的weakSelf，延迟2秒在主队列执行，调用weakSelf中的assertNotDealloc方法，方法还能响应的话就记录相关信息 类结构NSObject UIViewController UINavigationController UIPageViewController UISplitViewController UITabBarControllerUIView 检测对象中存在继承关系，检测方法也使用了继承关系 代码解析 NSObject (MemoryLeak) willDealloc 如果在白名单中，不进行检测 如果泄漏对象是最近一次UIControl事件的触发者，不进行检测（按照修改记录来看，当使用Button来pop ViewController的时候，VC不能及时释放） - (BOOL)willDealloc { NSString *className = NSStringFromClass([self class]); if ([[NSObject classNamesWhitelist] containsObject:className]) return NO; NSNumber *senderPtr = objc_getAssociatedObject([UIApplication sharedApplication], kLatestSenderKey); if ([senderPtr isEqualToNumber:@((uintptr_t)self)]) return NO; __weak id weakSelf = self; dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ __strong id strongSelf = weakSelf; [strongSelf assertNotDealloc]; }); return YES; }UIApplication (MemoryLeak) 获取和更新LatestSender - (BOOL)swizzled_sendAction:(SEL)action to:(id)target from:(id)sender forEvent:(UIEvent *)event { objc_setAssociatedObject(self, kLatestSenderKey, @((uintptr_t)sender), OBJC_ASSOCIATION_RETAIN); return [self swizzled_sendAction:action to:target from:sender forEvent:event]; }UITouch (MemoryLeak) 获取和更新LatestSender - (void)swizzled_setView:(UIView *)view { [self swizzled_setView:view]; if (view) { objc_setAssociatedObject([UIApplication sharedApplication], kLatestSenderKey, @((uintptr_t)view), OBJC_ASSOCIATION_RETAIN); } } assertNotDealloc 判断该对象是否已经在泄漏对象的集合里 添加到泄漏对象的集合里 内存泄漏提示 - (void)assertNotDealloc { if ([MLeakedObjectProxy isAnyObjectLeakedAtPtrs:[self parentPtrs]]) { return; } [MLeakedObjectProxy addLeakedObject:self]; NSString *className = NSStringFromClass([self class]); NSLog(@"Possibly Memory Leak.\nIn case that %@ should not be dealloced, override -willDealloc in %@ by returning NO.\nView-ViewController stack: %@", className, className, [self viewStack]); } willReleaseChildren 遍历视图树，构建视图堆栈ViewStack 记录父节点 - (void)willReleaseChildren:(NSArray *)children { NSArray *viewStack = [self viewStack]; NSSet *parentPtrs = [self parentPtrs]; for (id child in children) { NSString *className = NSStringFromClass([child class]); [child setViewStack:[viewStack arrayByAddingObject:className]]; [child setParentPtrs:[parentPtrs setByAddingObject:@((uintptr_t)child)]]; [child willDealloc]; } } UINavigationController (MemoryLeak) willDealloc 检测self.viewControllers - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.viewControllers]; return YES; } UIPageViewController (MemoryLeak) willDealloc 检测self.viewControllers - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.viewControllers]; return YES; } UISplitViewController (MemoryLeak) willDealloc 检测self.viewControllers - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.viewControllers]; return YES; } UITabBarController (MemoryLeak) willDealloc 检测self.viewControllers - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.viewControllers]; return YES; } UIViewController (MemoryLeak) willDealloc 检测self.childViewControllers 检测self.presentedViewController viewDidLoad的情况下从self.view开始遍历subviews - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.childViewControllers]; [self willReleaseChild:self.presentedViewController]; if (self.isViewLoaded) { [self willReleaseChild:self.view]; } return YES; } UIView (MemoryLeak) willDealloc 遍历view的subviews UIView (MemoryLeak) - (BOOL)willDealloc { if (![super willDealloc]) { return NO; } [self willReleaseChildren:self.subviews]; return YES; } 引用MLeaksFinder Github MLeaksFinder 新特性 MLeaksFinder：精准 iOS 内存泄漏检测工具 |
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