Question

我有多个操作（它们是AFNetworking请求），其中包含需要一些时间执行的完成块，以及需要在所有请求结束时保存的Core Data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];

当然，这并不是我想要的，因为请求是异步的。我试着像这样添加一个NSOperationQueue：

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];

这看起来好一点。使用waitUntilAllOperationsAreFinished，我的队列阻止当前线程，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。

关于如何以良好的方式实现这一目标的任何想法？

Answer 1

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];

Answer 2

AFNetworking设计了这种操作的方法，摘自GCD：

-enqueueBatchOfHTTPRequestOperationsWithRequests:progressBlock:completionBlock:

-enqueueBatchOfHTTPRequestOperations:progressBlock:completionBlock:

查看FAQ

Answer 3

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];

引用文档：http://cocoadocs.org/docsets/AFNetworking/2.5.0/

Answer 4

我的要求是来自String（URL）

数组的许多请求

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)
    })

}

显然，这样就可以级联调用，而不是N个异步调用。

等到多个网络请求都已执行 - 包括完成块

4 个答案: