iOS delegate線程引發(fā)的思考

在代理模式中，當obj1通過delegate委托obj2執(zhí)行某個操作時议蟆，我們會對委托執(zhí)行回調(diào)的線程感興趣。

先定義一個viewcontroller作為obj1,在其中執(zhí)行循環(huán)委托TestViewController去執(zhí)行委托

#import "ViewController.h"
#import "TestViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [testObject shareInstance];
    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    [btn setBackgroundColor:[UIColor redColor]];
    [btn addTarget:self action:@selector(pushNavigate) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    [self touchEvent];
    // Do any additional setup after loading the view.
}
-(void)pushNavigate{
    TestViewController *vc = [[TestViewController alloc] init];
    vc.view.backgroundColor = [UIColor greenColor];
    [self.navigationController pushViewController:vc animated:YES];
}

-(void)touchEvent{
    dispatch_queue_t q = dispatch_queue_create("threadTest", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(q, ^{
        if([[testObject shareInstance].testDelegate respondsToSelector:@selector(delegatePrint:)]) {
            NSLog(@"in loop1%@",[NSThread currentThread]);
            
            [[testObject shareInstance].testDelegate delegatePrint:@"test"];
        }
    });

    [self performSelector:@selector(touchEvent) withObject:nil afterDelay:1];
}

@end

新建一個委托中間人萎战，一個單例

static testObject *share;
@implementation testObject
+(instancetype)shareInstance;
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        share = [[super alloc] init];
    });
    return share;
}
@end

再看下被委托人obj2 的內(nèi)容咐容，很簡單的一個委托方法

#import "TestViewController.h"

@interface TestViewController ()

@end

@implementation TestViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [testObject shareInstance].testDelegate = self;
    // Do any additional setup after loading the view.
}

-(void)delegatePrint:(NSString *)value;
{
    UILabel *lable = [self.view viewWithTag:99];
    lable.text = value;
    NSLog(@"in loop2%@",[NSThread currentThread]);
}


@end

不管obj1在哪個線程中對代理人派發(fā)委托事件，obj2委托執(zhí)行的線程和派發(fā)時線程一致

2019-09-11 11:09:23.706339+0800 xcodeTest[33110:499973] in loop1<NSThread: 0x600003b16700>{number = 4, name = (null)}
2019-09-11 11:09:23.706691+0800 xcodeTest[33110:499973] in loop2<NSThread: 0x600003b16700>{number = 4, name = (null)}

所以啊蚂维，這里有個地方要注意戳粒，在使用代理的時候，代理派發(fā)的線程不確定時虫啥，有些UI主線程的修改蔚约，最好就用block包起來

    dispatch_async(dispatch_get_main_queue(), ^{
        UILabel *lable = [self.view viewWithTag:99];
        lable.text = value;
    });

可以看到obj2的lable更新了

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