强引用（强持有）

强引用（强持有）

解决NSTimer强引用:

• 重写didMoveToParentViewController方法

- (void)didMoveToParentViewController:(UIViewController *)parent{  
    // 无论push 进来 还是 pop 出去 正常跑  
    // 就算继续push 到下一层 pop 回去还是继续  
    if (parent == nil) {  
       [self.timer invalidate];  
        self.timer = nil;  
        NSLog(@"timer 走了");  
    }  
}  

• 定义timer时，采用闭包的形式，因此不需要指定target

- (void)blockTimer{  
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 repeats:YES block:^(NSTimer * _Nonnull timer) {  
        NSLog(@"timer fire - %@",timer);  
    }];  
}  

解决 强引用（强持有）

依赖中介者模式，打破强持有，其中推荐思路四

1. pop时在其他方法中销毁timer

- (void)didMoveToParentViewController:(UIViewController *)parent{  
    // 无论push 进来 还是 pop 出去 正常跑  
    // 就算继续push 到下一层 pop 回去还是继续  
    if (parent == nil) {  
       [self.timer invalidate];  
        self.timer = nil;  
        NSLog(@"timer 走了");  
    }  
}  

2.中介者模式，即不使用self，依赖于其他对象

//**********1、定义其他对象**********  
@property (nonatomic, strong) id            target;  

//**********1、修改target**********  
self.target = [[NSObject alloc] init];  
class_addMethod([NSObject class], @selector(fireHome), (IMP)fireHomeObjc, "v@:");  
self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self.target selector:@selector(fireHome) userInfo:nil repeats:YES];  

//**********3、imp**********  
void fireHomeObjc(id obj){  
    NSLog(@"%s -- %@",__func__,obj);  
}  

- (void)dealloc{  
    [self.timer invalidate];  
    self.timer = nil;  
    NSLog(@"%s",__func__);  
}  

3.自定义封装timer

//*********** .h文件 ***********  
@interface CJLTimerWapper : NSObject  

- (instancetype)cjl_initWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;  
- (void)cjl_invalidate;  

@end  

//*********** .m文件 ***********  
#import "CJLTimerWapper.h"  
#import <objc/message.h>  

@interface CJLTimerWapper ()  

@property(nonatomic, weak) id target;  
@property(nonatomic, assign) SEL aSelector;  
@property(nonatomic, strong) NSTimer *timer;  

@end  

@implementation CJLTimerWapper  

- (instancetype)cjl_initWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo{  
    if (self == [super init]) {  
        //传入vc  
        self.target = aTarget;  
        //传入的定时器方法  
        self.aSelector = aSelector;  
         
        if ([self.target respondsToSelector:self.aSelector]) {  
            Method method = class_getInstanceMethod([self.target class], aSelector);  
            const char *type = method_getTypeEncoding(method);  
            //给timerWapper添加方法  
            class_addMethod([self class], aSelector, (IMP)fireHomeWapper, type);  
            
            //启动一个timer，target是self，即监听自己  
            self.timer = [NSTimer scheduledTimerWithTimeInterval:ti target:self selector:aSelector userInfo:userInfo repeats:yesOrNo];  
        }  
    }  
    return self;  
}  

//一直跑runloop  
void fireHomeWapper(CJLTimerWapper *wapper){  
    //判断target是否存在  
    if (wapper.target) {  
        //如果存在则需要让vc知道，即向传入的target发送selector消息，并将此时的timer参数也一并传入，所以vc就可以得知`fireHome`方法，就这事这种方式定时器方法能够执行的原因
        //objc_msgSend发送消息，执行定时器方法  
        void (*lg_msgSend)(void *,SEL, id) = (void *)objc_msgSend;  
         lg_msgSend((__bridge void *)(wapper.target), wapper.aSelector,wapper.timer);  
    }else{  
        //如果target不存在，已经释放了，则释放当前的timerWrapper  
        [wapper.timer invalidate];  
        wapper.timer = nil;  
    }  
}  

//在vc的dealloc方法中调用，通过vc释放，从而让timer释放  
- (void)cjl_invalidate{  
    [self.timer invalidate];  
    self.timer = nil;  
}  

- (void)dealloc  
{
    NSLog(@"%s",__func__);  
}  

@end  

4. 利用NSProxy虚基类的子类

//************NSProxy子类************  
@interface CJLProxy : NSProxy  
+ (instancetype)proxyWithTransformObject:(id)object;  
@end  

@interface CJLProxy()  
@property (nonatomic, weak) id object;  
@end  

@implementation CJLProxy  
+ (instancetype)proxyWithTransformObject:(id)object{  
    CJLProxy *proxy = [CJLProxy alloc];  
    proxy.object = object;  
    return proxy;  
}  
-(id)forwardingTargetForSelector:(SEL)aSelector {  
    return self.object;     
}  

//************解决timer强持有问题************  
self.proxy = [CJLProxy proxyWithTransformObject:self];  
self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self.proxy selector:@selector(fireHome) userInfo:nil repeats:YES];  

//在dealloc中将timer正常释放  
- (void)dealloc{  
    [self.timer invalidate];  
    self.timer = nil;  
}