iOS7 Programming Cookbook 第七章学习笔记

####Accessing Variables in Block Objects
//访问block对象

typedef void (^BlockWithNoParams)(void);
- (void) scopeTest{
    NSInteger integer = -101;
    NSUInteger unsignedInteger = 101;

    NSLog(@"测试32位，64位 展示 %zd %tu",integer,unsignedInteger);
    
    __block NSUInteger integerValue = 10;
    
    //创建
    BlockWithNoParams myBlock = ^{
        NSLog(@"Integer value inside the block = %lu",
              (unsigned long)integerValue);
    };
    
    integerValue = 20;
    
    /* 更改integerValue变量为20，初始为10 */
    myBlock();
    
    NSLog(@"Integer value outside the block = %lu",
          (unsigned long)integerValue);
}

####Constructing Block Objects
//构建block对象

//定义 返回字符串，传入NSUInteger
typedef NSString* (^IntToStringConverter)(NSUInteger paramInteger);

- (NSString *) convertIntToString:(NSUInteger)paramInteger
                 usingBlockObject:(IntToStringConverter)paramBlockObject{
    return paramBlockObject(paramInteger);
}

//执行转换
- (void) doTheConversion{
    
    NSString *result = [self convertIntToString:123 usingBlockObject:^NSString *(NSUInteger paramInteger) {
                NSString *result = [NSString stringWithFormat:@"%lu",(unsigned long)paramInteger];
                return result;
            }];
    
    NSLog(@"result = %@", result);
    
}

####Constructing Your Own Dispatch Queues with GCD
//在线程里构建调度队列

/* 1 */
void firstIteration(void *paramContext);
void secondIteration(void *paramContext);
void thirdIteration(void *paramContext);

/* 2 */
void firstIteration(void *paramContext){
    NSUInteger counter = 0;
    for (counter = 0;counter < 5; counter++){
        NSLog(@"First iteration, counter = %lu", (unsigned long)counter);
    }
}

void secondIteration(void *paramContext){
    NSUInteger counter = 0;
    for (counter = 0;counter < 5; counter++){
        NSLog(@"Second iteration, counter = %lu", (unsigned long)counter);
    }
}

void thirdIteration(void *paramContext){
    NSUInteger counter = 0;
    for (counter = 0; counter < 5; counter++){
        NSLog(@"Third iteration, counter = %lu", (unsigned long)counter);
    }
}

//创建一个新的调度队列模块
dispatch_queue_t firstSerialQueue = dispatch_queue_create("com.pixolity.GCD.serialQueue1", 0);
//函数的异步执行调度队列
dispatch_async_f(firstSerialQueue, NULL, firstIteration);
dispatch_async_f(firstSerialQueue, NULL, secondIteration);
dispatch_async_f(firstSerialQueue, NULL, thirdIteration);

####Creating Concurrency with Threads
//并发线程

- (void) autoreleaseThread:(id)paramSender{
    
    @autoreleasepool {
        NSBundle *mainBundle = [NSBundle mainBundle];
        //从resource读取图片
        NSString *filePath = [mainBundle pathForResource:@"MacBookAir" ofType:@"png"];
        
        UIImage *image = [UIImage imageWithContentsOfFile:filePath];
        
        NSLog(@"Image = %@", image);
    }
    
}

- (void)viewDidLoad {
    
    [super viewDidLoad];
    //另开线程读取图片
    [NSThread detachNewThreadSelector:@selector(autoreleaseThread:)toTarget:self withObject:self];
    
}

####Creating Timers
//NSTimer

@interface AppDelegate ()
@property (nonatomic, strong) NSTimer *paintingTimer;
@end

- (void) paint:(NSTimer *)paramTimer{
    /* Do something here */
    NSLog(@"Painting");
}

- (void) startPainting{
    //选择器调用
    SEL selectorToCall = @selector(paint:);
    
    //组成一个方法签名的选择器，我们知道选择器是当前类，所以它是很容易构造方法签名
    //instanceMethodSignatureForSelector :返回一个NSMethodSignature对象,该对象包含一个实例的描述方法被给定的选择器。
    NSMethodSignature *methodSignature = [[self class] instanceMethodSignatureForSelector:selectorToCall];
    
    //NSInvocation是一个objective - c消息呈现静态的,也就是说,它是一个行动变成了一个对象。NSInvocation对象用于存储和转发消息之间的对象和应用程序,主要由NSTimer对象和分布式对象系统。
    //调用方法签名，安排一个计时器
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
    [invocation setTarget:self];
    [invocation setSelector:selectorToCall];
    
    //创建并返回一个新的NSTimer对象使用指定的调用初始化对象。
    self.paintingTimer = [NSTimer timerWithTimeInterval:1.0
                                             invocation:invocation
                                                repeats:YES];;
    
    //为安排计时器运行循环
    [[NSRunLoop currentRunLoop] addTimer:self.paintingTimer
                                 forMode:NSDefaultRunLoopMode];
    
}

//停止方法
- (void) stopPainting{
    if (self.paintingTimer != nil){
    //不为空，停止时间
        [self.paintingTimer invalidate];
    }
}

//后台
- (void)applicationWillResignActive:(UIApplication *)application{
    [self stopPainting];
}

//进入前台
- (void)applicationDidBecomeActive:(UIApplication *)application{
    [self startPainting];
}

####Exiting Threads and Timers
//NSThread

@property (nonatomic, strong) NSThread *myThread;

- (void) threadEntryPoint{
    
    @autoreleasepool {
        NSLog(@"线程入口");
        while ([[NSThread currentThread] isCancelled] == NO){
            //停4秒
            [NSThread sleepForTimeInterval:4];
            if ([[NSThread currentThread] isCancelled] == NO){
                NSLog(@"线程循环");
            }
        }
        NSLog(@"线程完成");
    }
    
}


- (void) stopThread{
//取消线程
    [self.myThread cancel];
    self.myThread = nil;
    
}

//线程入口点
    self.myThread = [[NSThread alloc]
                     initWithTarget:self
                     selector:@selector(threadEntryPoint)
                     object:nil];
//停止线程
    [self performSelector:@selector(stopThread) withObject:nil afterDelay:3.0f];
                     
    [self.myThread start];

####Grouping Tasks Together with GCD
//GCD

void reloadAllComponents(void *context);
- (void) reloadTableView{
    NSLog(@"%s", __FUNCTION__);
}

- (void) reloadScrollView{
    NSLog(@"%s", __FUNCTION__);
}

- (void) reloadImageView{
    NSLog(@"%s", __FUNCTION__);
}

void reloadAllComponents(void *context){
    
    AppDelegate *self = (__bridge AppDelegate *)context;
    
    [self reloadTableView];
    [self reloadScrollView];
    [self reloadImageView];
    
}

    //任务组线程
    dispatch_group_t taskGroup =  dispatch_group_create();
    //主线程
    dispatch_queue_t mainQueue =  dispatch_get_main_queue();
    //__bridge只做类型转换，不修改对象
    dispatch_group_async_f(taskGroup,
                           mainQueue,
                           (__bridge void *)self,
                           reloadAllComponents);
    
    //当我们完成，执行下面block
    dispatch_group_notify(taskGroup, mainQueue, ^{
        [[[UIAlertView alloc] initWithTitle:@"Finished"
                                    message:@"All tasks are finished"
                                   delegate:nil
                          cancelButtonTitle:@"OK"
                          otherButtonTitles:nil, nil] show];
        
    });

Reference

• O’Reilly Shop iOS 7 Programming Cookbook