ios NSURLConnection sendAsynchronousRequest:queue:completionHandler：连续发出多个请求？
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NSURLConnection sendAsynchronousRequest:queue:completionHandler: making multiple requests in a row?
提问by Nic Hubbard
I have been using NSURLConnection'ssendAsynchronousRequest:queue:completionHandler:method which is great. But, I now need to make multiple requests in a row.
我一直在使用NSURLConnection'ssendAsynchronousRequest:queue:completionHandler:很棒的方法。但是，我现在需要连续发出多个请求。
How can I do this while still using this great asychronous method?
如何在仍然使用这种出色的异步方法的同时做到这一点？
回答by yuji
There's lots of ways you can do this depending on the behavior you want.
根据您想要的行为，有很多方法可以做到这一点。
You can send a bunch of asynchronous requests at once, track the number of requests that have been completed, and do something once they're all done:
您可以一次发送一堆异步请求，跟踪已完成的请求数量，并在它们全部完成后做一些事情：
NSInteger outstandingRequests = [requestsArray count];
for (NSURLRequest *request in requestsArray) {
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
[self doSomethingWithData:data];
outstandingRequests--;
if (outstandingRequests == 0) {
[self doSomethingElse];
}
}];
}
You could chain the blocks together:
您可以将这些块链接在一起：
NSMutableArray *dataArray = [NSMutableArray array];
__block (^handler)(NSURLResponse *response, NSData *data, NSError *error);
NSInteger currentRequestIndex = 0;
handler = ^{
[dataArray addObject:data];
currentRequestIndex++;
if (currentRequestIndex < [requestsArray count]) {
[NSURLConnection sendAsynchronousRequest:[requestsArray objectAtIndex:currentRequestIndex]
queue:[NSOperationQueue mainQueue]
completionHandler:handler];
} else {
[self doSomethingElse];
}
};
[NSURLConnection sendAsynchronousRequest:[requestsArray objectAtIndex:0]
queue:[NSOperationQueue mainQueue]
completionHandler:handler];
Or you could do all the requests synchronously in an ansynchronous block:
或者您可以在异步块中同步执行所有请求：
dispatch_queue_t callerQueue = dispatch_get_current_queue();
dispatch_queue_t downloadQueue = dispatch_queue_create("Lots of requests", NULL);
dispatch_async(downloadQueue, ^{
for (NSRURLRequest *request in requestsArray) {
[dataArray addObject:[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]];
}
dispatch_async(callerQueue, ^{
[self doSomethingWithDataArray:dataArray];
});
});
});
P.S. If you use any of these you should add some error checking.
PS 如果您使用其中任何一个，您应该添加一些错误检查。
