- (IBAction)getImage:(id)sender {
//1,准备URL
NSString *str = @"http://e.hiphotos.baidu.com/image/h%3D1200%3Bcrop%3D0%2C0%2C1920%2C1200/sign=e13d66699825bc31345d059a6eefb6d2/6159252dd42a2834f85385ac5ab5c9ea14cebfa4.jpg";
NSURL *url = [NSURL URLWithString:str];
//2，创建请求对象
NSURLRequest *request = [NSURLRequest requestWithURL:url];
//链接对象，block 异步
__block MXTViewController *weakSelf = self;
NSOperationQueue *queue = [[NSOperationQueue new] autorelease];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
//获取data
UIImage *image = [UIImage imageWithData:data];
//回到主线程更新页面
dispatch_sync( dispatch_get_main_queue(), ^{
//block 不可以使用_imageView 的方式访问属性，会造成self 引用计数+1 ,不能使用强引用
//要使用weak
weakSelf.imageView.image = image;
});
}];