ImageDownLoaderAndKVO

//开始下载
- (IBAction)startDownLoader:(id)sender {
    
    self.imageDownLoader = [[ImageDownLoader alloc] initWithImageURL:kPicURL delegate:self];
}
//实现方法
-(void)imageDownLoader:(ImageDownLoader *)imageDownLoader didSuccessedWithImage:(UIImage *)image
{
    self.imageView.image = image;
}

//结束下载
- (IBAction)cancelDownLoader:(id)sender {
    
    [self.imageDownLoader cancel];
}

//初始化方法
-(id)initWithImageURL:(NSString *)imageURL delegate:(id<imageDownLoaderDelegate>)delegate
{
    self = [super init];
    if (self) {
        //给delegate 赋值
        self.delegate = delegate;
        
        //进行请求
        [self requestImageWithImageURL:imageURL];
    }
    return self;
}

//取消下载
-(void)cancel
{
    [self.connection cancel];
}


-(void)requestImageWithImageURL:(NSString *)imageURL
{
    
    //1.创建URL
    //再编码
    NSString *newStr = [imageURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    //创建
    NSURL *url = [NSURL URLWithString:newStr];
    
    //2.创建请求对象
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    //3.请求并设置代理
    self.connection = [NSURLConnection connectionWithRequest:request delegate:self];
    
    
}

//链接到服务器
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if (_data == nil) {
        self.data = [NSMutableData data];
    }
}

//获取数据
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //拼接
    [_data appendData:data];
    //进行数据操作
}

//下载完成
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
 
    //转化图片
    UIImage *image = [UIImage imageWithData:_data];
    //通知代理 将图片拿走
    [_delegate imageDownLoader:self didSuccessedWithImage:image];

}

//给person对象添加观察者
    [self.person addObserver:self forKeyPath:@"name" options:(NSKeyValueObservingOptionNew) context:@"西兰花"];

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSLog(@"keyPath : %@",keyPath);
    NSLog(@"object : %@",object);
    NSLog(@"change :%@",change);
    NSLog(@"context : %@",context);
    
    
    self.view.backgroundColor = [UIColor colorWithRed:arc4random() % 256 / 255.0 green:arc4random() % 256 / 255.0 blue:arc4random() % 256 / 255.0 alpha:1.0];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self.nameTf endEditing:YES];
    
    //使用输入框内的名字 给person对象赋值
    self.person.name = self.nameTf.text;
    
    //[self.nameTf resignFirstResponder];
}