18-内存管理 01（定时器）

一、定时器

--------------------------------------------------MJProxy.h------------------------------------------------
#import 

@interface MJProxy : NSObject
+ (instancetype)proxyWithTarget:(id)target;
@property (weak, nonatomic) id target;
@end
--------------------------------------------------MJProxy.m---------------------------------------------
#import "MJProxy.h"

@implementation MJProxy

+ (instancetype)proxyWithTarget:(id)target
{
    MJProxy *proxy = [[MJProxy alloc] init];
    proxy.target = target;
    return proxy;
}

//消息转发
- (id)forwardingTargetForSelector:(SEL)aSelector
{
    return self.target;
}

@end
---------------------------------------------------ViewController.m-------------------------------------------
#import "ViewController.h"
#import "MJProxy.h"

@interface ViewController ()
@property (strong, nonatomic) CADisplayLink *link;
@property (strong, nonatomic) NSTimer *timer;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 保证调用频率和屏幕的刷帧频率一致，60FPS
    self.link = [CADisplayLink displayLinkWithTarget:[MJProxy proxyWithTarget:self] selector:@selector(linkTest)];
    [self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
    
//    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[MJProxy proxyWithTarget:self] selector:@selector(timerTest) userInfo:nil repeats:YES];
    
//    __weak typeof(self) weakSelf = self;
//    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 repeats:YES block:^(NSTimer * _Nonnull timer) {
//        [weakSelf timerTest];
//    }];
}

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

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

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

@end

• NSProxy

------------------------------------------MJProxy.h---------------------------------------
#import 

//NSProxy：专门用来消息转发
@interface MJProxy : NSProxy
+ (instancetype)proxyWithTarget:(id)target;
@property (weak, nonatomic) id target;
@end
-------------------------------------------MJProxy.m---------------------------------------
#import "MJProxy.h"

@implementation MJProxy

+ (instancetype)proxyWithTarget:(id)target
{
    // NSProxy对象不需要调用init，因为它本来就没有init方法
    MJProxy *proxy = [MJProxy alloc];
    proxy.target = target;
    return proxy;
}

//1.根据sel查找当前类中有没有sel方法，有的话直接调用该方法，不会进行消息转发。
//2.没有的话直接进行消息转发，不再去父类中查找，执行效率高。
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel
{
    return [self.target methodSignatureForSelector:sel];
}

- (void)forwardInvocation:(NSInvocation *)invocation
{
    [invocation invokeWithTarget:self.target];
}
@end
--------------------------------------------ViewController.m---------------------------------------------
#import "ViewController.h"
#import "MJProxy.h"
#import "MJProxy1.h"

@interface ViewController ()
@property (strong, nonatomic) NSTimer *timer;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[MJProxy proxyWithTarget:self] selector:@selector(timerTest) userInfo:nil repeats:YES];
}

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

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

@end

二、GCD定时器

GCD定时器操作的系统内核，比NSTimer准时;当有scrollview滚动时不受影响。

对GCD定时器的封装

--------------------------------------------MJTimer.h--------------------------------------
#import 

@interface MJTimer : NSObject

+ (NSString *)execTask:(void(^)(void))task
           start:(NSTimeInterval)start
        interval:(NSTimeInterval)interval
         repeats:(BOOL)repeats
           async:(BOOL)async;

+ (NSString *)execTask:(id)target
              selector:(SEL)selector
                 start:(NSTimeInterval)start
              interval:(NSTimeInterval)interval
               repeats:(BOOL)repeats
                 async:(BOOL)async;

+ (void)cancelTask:(NSString *)name;

@end
--------------------------------------------MJTimer.m--------------------------------------------
#import "MJTimer.h"

@implementation MJTimer

static NSMutableDictionary *timers_;
dispatch_semaphore_t semaphore_;
+ (void)initialize
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        timers_ = [NSMutableDictionary dictionary];
        semaphore_ = dispatch_semaphore_create(1);
    });
}

+ (NSString *)execTask:(void (^)(void))task start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async
{
    if (!task || start < 0 || (interval <= 0 && repeats)) return nil;
    
    // 队列
    dispatch_queue_t queue = async ? dispatch_get_global_queue(0, 0) : dispatch_get_main_queue();
    
    // 创建定时器
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    
    // 设置时间 start:几秒后开始执行  interval：每隔多久执行一次
    dispatch_source_set_timer(timer,
                              dispatch_time(DISPATCH_TIME_NOW, start * NSEC_PER_SEC),
                              interval * NSEC_PER_SEC, 0);
    
    
    dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
    // 定时器的唯一标识
    NSString *name = [NSString stringWithFormat:@"%zd", timers_.count];
    // 存放到字典中
    timers_[name] = timer;
    dispatch_semaphore_signal(semaphore_);
    
    // 设置回调
    dispatch_source_set_event_handler(timer, ^{
        task();
        
        if (!repeats) { // 不重复的任务
            [self cancelTask:name];
        }
    });
    
    // 启动定时器
    dispatch_resume(timer);
    
    return name;
}

+ (NSString *)execTask:(id)target selector:(SEL)selector start:(NSTimeInterval)start interval:(NSTimeInterval)interval repeats:(BOOL)repeats async:(BOOL)async
{
    if (!target || !selector) return nil;
    
    return [self execTask:^{
        if ([target respondsToSelector:selector]) {
            //消除XCode警告
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
            [target performSelector:selector];
#pragma clang diagnostic pop
        }
    } start:start interval:interval repeats:repeats async:async];
}

+ (void)cancelTask:(NSString *)name
{
    if (name.length == 0) return;
    
    dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER);
    
    dispatch_source_t timer = timers_[name];
    if (timer) {
        dispatch_source_cancel(timer);
        [timers_ removeObjectForKey:name];
    }

    dispatch_semaphore_signal(semaphore_);
}

@end