iOS响应链打印日志确认

苹果官方给的响应链示意图如下所示：

用文字描述的话就是：
subView->UIView->(UIViewController)->UIWindow->UIApplication->UIApplicationDelegate

自定义一个视图，重写touchesBegan:withEvent:方法:

#import <UIKit/UIKit.h>

@interface MyTouch : UIView

@end

@implementation MyTouch

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];
    NSLog(@"This is my touch!");
}

@end

在ViewController的view中添加一个MyTouch视图：

- (void)viewDidLoad {
    [super viewDidLoad];
    
    MyTouch *my = [[MyTouch alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    my.backgroundColor = [UIColor redColor];
    [self.view addSubview:my];
}

建立符号断点，并在断点处打印$arg1的值：

符号断点

运行项目，查看打印日志：

<MyTouch: 0x7fbba5e17b10; frame = (0 0; 100 100); layer = <CALayer: 0x60400002e900>>

<UIView: 0x7fbba5e18400; frame = (0 0; 375 812); autoresize = W+H; layer = <CALayer: 0x604000232bc0>>

<ViewController: 0x7fbba5d058f0>

<UIWindow: 0x7fbba5f02f20; frame = (0 0; 375 812); gestureRecognizers = <NSArray: 0x600000251310>; layer = <UIWindowLayer: 0x60400003ad00>>

<UIApplication: 0x7fbba5e00000>

<AppDelegate: 0x600000036240>

2018-12-20 17:22:21.361654+0800 Current[41380:15485776] This is my touch!

可以看到响应链为MyTouch->UIView->ViewController->UIWindow->UIApplication->AppDelegate，与文档描述一致。