[iOS] 监视某个VC生命周期函数

Question

RT 需求是我要创建一个桥接类。我需要对一些VC的生命周期做一些监控，比如VC的viewWillAppear等生命周期函数执行完，执行我的方法。 目前已尝试过 协议 hook 但都不够实现我的需求。协议 并不能强制要求所有这些V...

巴扎黑 · Answer

Use method swizzling, example:

#import "UIViewController+WJAdd.h"
#import 

typedef void (* _IMP)(id,SEL,...);

@implementation UIViewController (WJAdd)

+(void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Method viewDidLoad=class_getInstanceMethod(self, @selector(viewDidLoad));

        _IMP viewDidLoad_IMP=(_IMP)method_getImplementation(viewDidLoad);
        method_setImplementation(viewDidLoad, imp_implementationWithBlock(^(id target,SEL action){
            viewDidLoad_IMP(target,@selector(viewDidLoad));
            NSLog(@"%@ did load",target);
            [target dosomething];
        }));
    });

}

怪我咯 · Answer

Thank you for your answer

But why was it replaced multiple times? The code is as follows

@implementation HookTest
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

+(void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        
        Method viewDidAppear=class_getInstanceMethod([HookTest class], @selector(viewDidAppear:));
        
        _IMP viewDidAppear_IMP=(_IMP)method_getImplementation(viewDidAppear);
        method_setImplementation(viewDidAppear, imp_implementationWithBlock(^(id target,SEL action){
            viewDidAppear_IMP(target,@selector(viewDidAppear:));
            NSLog(@"%@ did load",target);
//            [target dosomething];
        }));
    });
    
}

The log is as follows