iOS networking（二） http异步队列请求
同步队列请求
#pragma mark -异步队列请求
-(void)requestByAsyncQueue{
NSURLRequest *req = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://localhost:8001"]];
NSURLResponse *resp;
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
// NSOperationQueue *queue = [NSOperationQueue mainQueue];
//发送异步请求
[NSURLConnection sendAsynchronousRequest:req queue:queue completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
//检查错误
if (connectionError) {
NSLog(@"%@",connectionError);
NSLog(@"==resq====%@",resp);
return;
}
//检验状态码
if ([resp isKindOfClass:[NSHTTPURLResponse class]]) {
if (((NSHTTPURLResponse *)resp).statusCode != 200) {
return;
}
}
//解析json
NSLog(@"%@",[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil ]);
NSLog(@"====请求结束====");
}];
NSLog(@"====请求开始1====");
}
打印出的日志
2016-02-04 09:21:38.858 network-demo[27091:3621428] 2016-02-04 01:21:38 +0000
2016-02-04 09:21:39.858 network-demo[27091:3621428] 2016-02-04 01:21:39 +0000
2016-02-04 09:21:40.462 network-demo[27091:3621950] ====请求开始1====
2016-02-04 09:21:40.858 network-demo[27091:3621428] 2016-02-04 01:21:40 +0000
2016-02-04 09:21:41.858 network-demo[27091:3621428] 2016-02-04 01:21:41 +0000
2016-02-04 09:21:42.859 network-demo[27091:3621428] 2016-02-04 01:21:42 +0000
2016-02-04 09:21:43.417 network-demo[27091:3621966] {
age = 20;
name = xxx;
}
2016-02-04 09:21:43.417 network-demo[27091:3621966] ====请求结束1====
2016-02-04 09:21:43.859 network-demo[27091:3621428] 2016-02-04 01:21:43 +0000
2016-02-04 09:21:44.859 network-demo[27091:3621428] 2016-02-04 01:21:44 +0000
从这里可以看出，请求是异步的，并且可以NSOperationQueue可以和NSInvocationOperation或是NSBlocknOperation混合使用。我们再来测试下在使用主队列 NSOperationQueue *queue = [NSOperationQueue mainQueue]; 执行请求，会不会阻塞主进程
2016-02-04 16:10:59.532 network-demo[29228:3818310] 2016-02-04 08:10:59 +0000
2016-02-04 16:10:59.793 network-demo[29228:3818310] ====请求开始1====
2016-02-04 16:11:00.532 network-demo[29228:3818310] 2016-02-04 08:11:00 +0000
2016-02-04 16:11:01.532 network-demo[29228:3818310] 2016-02-04 08:11:01 +0000
2016-02-04 16:11:02.531 network-demo[29228:3818310] 2016-02-04 08:11:02 +0000
2016-02-04 16:11:03.532 network-demo[29228:3818310] 2016-02-04 08:11:03 +0000
2016-02-04 16:11:04.532 network-demo[29228:3818310] 2016-02-04 08:11:04 +0000
2016-02-04 16:11:05.531 network-demo[29228:3818310] 2016-02-04 08:11:05 +0000
2016-02-04 16:11:06.532 network-demo[29228:3818310] 2016-02-04 08:11:06 +0000
2016-02-04 16:11:07.532 network-demo[29228:3818310] 2016-02-04 08:11:07 +0000
2016-02-04 16:11:08.532 network-demo[29228:3818310] 2016-02-04 08:11:08 +0000
2016-02-04 16:11:09.532 network-demo[29228:3818310] 2016-02-04 08:11:09 +0000
2016-02-04 16:11:09.942 network-demo[29228:3818310] {
age = 20;
name = xxx;
}
2016-02-04 16:11:09.942 network-demo[29228:3818310] ====请求结束1====
2016-02-04 16:11:10.532 network-demo[29228:3818310] 2016-02-04 08:11:10 +0000
2016-02-04 16:11:11.532 network-demo[29228:3818310] 2016-02-04 08:11:11 +0000
可以从打印结果看出，并不会造成主线程的阻塞。 我们再来试下在completionHandler中加入sleep(5),看看会不会阻塞线程
//发送异步请求
[NSURLConnection sendAsynchronousRequest:req queue:queue completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
NSLog(@"====deno star====");
sleep(5);
NSLog(@"====sleep deno ====");
//检查错误
if (connectionError) {
NSLog(@"%@",connectionError);
NSLog(@"==resq====%@",resp);
return;
}
//检验状态码
if ([resp isKindOfClass:[NSHTTPURLResponse class]]) {
if (((NSHTTPURLResponse *)resp).statusCode != 200) {
return;
}
}
//解析json
NSLog(@"%@",[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil ]);
NSLog(@"====请求结束1====");
}];
可以发现，线程被阻塞了。这就说明一个问题，在发送sendAsynchronousRequest异步请求后，都是异步调用，queue参数只是说明在哪个队列上执行completionHandler这个block而已。
关于NSOperationQueue的部分，就不多说了，之前的文章写过，见这里
异步队列请求的最佳实践
- 返回响应的数据都会保存在内存中，如果响应的内容非常大，请考虑内存溢出的问题。
- 在处理返回数据前，请验证error和http响应状态码
- 不能使用网络请求的高级功能，如验证，进度，流传输,取消
demo
感谢收看，如果对大家有帮助，请github上follow和star，本文发布在刘彦玮的技术博客，转载请注明出处
