GCD實戰一：使用串行隊列實現簡單的預加載

原創

2020-02-21 04:13

其主要思路是使用gcd創建串行隊列，然後在此隊列中先後執行兩個任務：1.預加載一個viewController 2.將這個viewController推入

代碼如下：

@implementation DWAppDelegate
{
    dispatch_queue_t _serialQueue;
    UINavigationController *_navController;
}

- (dispatch_queue_t)serialQueue
{
    if (!_serialQueue) {
        _serialQueue = dispatch_queue_create("serialQueue", DISPATCH_QUEUE_SERIAL);//創建串行隊列
    }
    return _serialQueue;
}

- (void)prepareViewController
{
    dispatch_async([self serialQueue], ^{//把block中的任務放入串行隊列中執行，這是第一個任務
        self.viewController = [[[DWViewController alloc] init] autorelease];
        sleep(2);//假裝這個viewController創建起來很花時間。。其實view都還沒加載，根本不花時間。
        NSLog(@"prepared");
    });
}

- (void)goToViewController
{
    dispatch_async([self serialQueue], ^{//第二個任務，推入viewController
        NSLog(@"go");
        dispatch_async(dispatch_get_main_queue(), ^{//涉及UI更新的操作，放入主線程中
            [_navController pushViewController:self.viewController animated:YES];
        });
    });
}

- (void)dealloc
{
    dispatch_release(_serialQueue);
    [_navController release];
    [_window release];
    [_viewController release];
    [super dealloc];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [self prepareViewController];
    
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    
    DWViewController *viewController = [[[DWViewController alloc] initWithNibName:@"DWViewController" bundle:nil] autorelease];
    viewController.view.backgroundColor = [UIColor blueColor];
    _navController = [[UINavigationController alloc] initWithRootViewController:viewController];
    self.window.rootViewController = _navController;
    
    [self goToViewController];
    
    [self.window makeKeyAndVisible];
    return YES;
}

工程下載：

gcdtest1.zip