ios 等到多个网络请求都执行完毕 - 包括它们的完成块
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原文地址: http://stackoverflow.com/questions/10643797/
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Wait until multiple networking requests have all executed - including their completion blocks
提问by choise
I have multiple operations (they're AFNetworking requests) with completion blocks that takes some time to execute, and a Core Data object that needs to be saved at the end of all?the requests.
我有多个操作（它们是 AFNetworking 请求），其中包含需要一些时间来执行的完成块，以及需要在所有请求结束时保存的核心数据对象。
MyCoreDataObject *coreDataObject;
AFHTTPRequestOperation *operation1 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation1 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute1 = responseObject;
sleep(5);
}];
[operation1 start];
AFHTTPRequestOperation *operation2 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation2 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute2 = responseObject;
sleep(10);
}];
[operation1 operation2];
[context save:nil];
Of course, this does not work as I want because the requests are asynchronous. I tried adding an NSOperationQueue like so:
当然，这并不像我想要的那样工作，因为请求是异步的。我尝试添加一个 NSOperationQueue 像这样：
NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
[operationQueue setMaxConcurrentOperationCount:2];
AFHTTPRequestOperation *operation1 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation1 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute1 = responseObject;
sleep(5);
}];
[operationQueue addOperation:operation1];
AFHTTPRequestOperation *operation2 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation2 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute2 = responseObject;
sleep(10);
}];
[operationQueue addOperation:operation2];
[imageQueue waitUntilAllOperationsAreFinished];
[context save:nil];
This looks a bit better. Using waitUntilAllOperationsAreFinished, my queue blocks the current thread until my requests are finished, but not until my success Blocks are finished, which is really what I need.
这看起来好一点。使用waitUntilAllOperationsAreFinished，我的队列阻塞当前线程，直到我的请求完成，但直到我的成功块完成，这才是我真正需要的。
Any ideas on how to achieve this in a good way?
关于如何以一种好的方式实现这一目标的任何想法？
回答by Ken Thomases
Use dispatch groups.
使用调度组。
dispatch_group_t group = dispatch_group_create();
MyCoreDataObject *coreDataObject;
dispatch_group_enter(group);
AFHTTPRequestOperation *operation1 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation1 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute1 = responseObject;
sleep(5);
dispatch_group_leave(group);
}];
[operation1 start];
dispatch_group_enter(group);
AFHTTPRequestOperation *operation2 = [[AFHTTPRequestOperation alloc] initWithRequest:request1];
[operation2 setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
coreDataObject.attribute2 = responseObject;
sleep(10);
dispatch_group_leave(group);
}];
[operation2 start];
dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
dispatch_release(group);
[context save:nil];
回答by wzs
AFNetworking has designed method for this kind of operations, which abstracts from GCD:
AFNetworking 为这种操作设计了方法，它从 GCD 中抽象出来：
-enqueueBatchOfHTTPRequestOperationsWithRequests:progressBlock:completionBlock:
-enqueueBatchOfHTTPRequestOperationsWithRequests:progressBlock:completionBlock:
-enqueueBatchOfHTTPRequestOperations:progressBlock:completionBlock:
-enqueueBatchOfHTTPRequestOperations:progressBlock:completionBlock:
Take a look at FAQ
看看常见问题
回答by yershuachu
I belive something like this:
我相信这样的事情：
NSMutableArray *mutableOperations = [NSMutableArray array];
for (NSURL *fileURL in filesToUpload) {
NSURLRequest *request = [[AFHTTPRequestSerializer serializer] multipartFormRequestWithMethod:@"POST" URLString:@"http://example.com/upload" parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
[formData appendPartWithFileURL:fileURL name:@"images[]" error:nil];
}];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[mutableOperations addObject:operation];
}
NSArray *operations = [AFURLConnectionOperation batchOfRequestOperations:@[...] progressBlock:^(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations) {
NSLog(@"%lu of %lu complete", numberOfFinishedOperations, totalNumberOfOperations);
} completionBlock:^(NSArray *operations) {
NSLog(@"All operations in batch complete");
}];
[[NSOperationQueue mainQueue] addOperations:operations waitUntilFinished:NO];
refering to docs: http://cocoadocs.org/docsets/AFNetworking/2.5.0/
回答by Luca Davanzo
My requirements were those of do many request from an array of String (URL)
我的要求是从字符串（URL）数组中执行许多请求
func updateSourceData(element: Int) {
if element > availableUrls.count - 1 {
return
}
let service = SourceDataServiceDao()
let currentUrl = availableUrls[element]
service.fooCall(url: currentUrl, completion: { (response, error) -> Void in
self.updateSourceData(element + 1)
})
}
Obviously, in this way calls are made in cascade, not N asynchronous calls.
显然，这种方式调用是级联进行的，而不是N个异步调用。
