[移动开发]对象dealloc监控demo

学习了部分runtime的知识后，准备动手做个有意思的东西来见证自己最近学习的成果。

就写一个debug环境下对象的监控的demo吧。

在OC中，所有对象均是继承来自NSObject，所以

实现步骤：

1.我们要利用Category创建一个NSObject的分类,就叫Debug.h吧，加入两个接口用来供外界启动检测。

2.延迟判断该对象是否正常销毁，需要创建一个服务类，为了避免服务类自身的循环引用，需要创建一个代理类来保存启动的服务对象（是否必要？__weak 代替），在服务类的初始化中初始化代理类，然后启动服务，

3.那怎么判断对象是否正常销毁呢？（使用关联对象将服务类的self绑定到目标对象，目标对象销毁，则self销毁，服务不启动），如果self未销毁，则启动服务，启动时，在代理类中可以使用消息转发机制获取服务类的对象。

代码exp：

//  NSObject+Debug.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSObject (Debug)

  //. 增加两个接口来判断对象是否正常销毁
- (void)judgeDeallocation;
- (void)judgeDeallocationAfterDelay:(NSTimeInterval)delay;

@end

NS_ASSUME_NONNULL_END

//  NSObject+Debug.m

#import "NSObject+Debug.h"
#import <Foundation/Foundation.h>
#import <objc/runtime.h>

@interface JudgeDeallocationTimerProxy : NSObject {
    __weak id helper;
}
@end

@implementation JudgeDeallocationTimerProxy

- (id)initWithHelper:(id)object {
    self = [super init];
    if (self) {
        helper = object;
    }
    return self;
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    return helper;
}

@end

@interface JudgeDeallocationHelper : NSObject {
    NSTimer *timer;
    JudgeDeallocationTimerProxy *proxy;
    __weak id object;
}
@property (retain, nonatomic) NSTimer *timer;
@property (retain, nonatomic) JudgeDeallocationTimerProxy *proxy;
+ (void)judgeDeallocation:(id)object afterDelay:(NSTimeInterval)delay;
@end

@implementation JudgeDeallocationHelper

@synthesize timer, proxy;

static const char JUDGE_DEALLOCATION_HELPER_KEY = 0;

+ (void)judgeDeallocation:(id)object afterDelay:(NSTimeInterval)delay {
#ifdef DEBUG
    [[self alloc] initWithObject:object withDelay:delay];
#endif
}

- (id)initWithObject:(id)anObject withDelay:(NSTimeInterval)delay {
    self = [super init];
  //  __weak __typeof(self)weakSelf = self;
    if (self) {
        object = anObject;
        objc_setAssociatedObject(object, &JUDGE_DEALLOCATION_HELPER_KEY, self, OBJC_ASSOCIATION_RETAIN);
        self.proxy = [[JudgeDeallocationTimerProxy alloc] initWithHelper:self];
        self.timer = [NSTimer scheduledTimerWithTimeInterval:delay
                                                      target:self.proxy
                                                    selector:@selector(judgeTrigger)
                                                    userInfo:nil
                                                     repeats:NO];
    }
    return self;
}

- (void)dealloc {
    [self.timer invalidate];
    self.timer = nil;
    self.proxy = nil;
}

- (void)judgeTrigger {
    NSLog(@"%@ dealloc is failed! Please check it!", NSStringFromClass([object class]));
}

@end


@implementation NSObject (Debug)

- (void)judgeDeallocation {
    [self judgeDeallocationAfterDelay:0];
}

- (void)judgeDeallocationAfterDelay:(NSTimeInterval)delay {
    [JudgeDeallocationHelper judgeDeallocation:self afterDelay:delay];
}

@end