sendAsynchronousRequest :queue:completionHandler:
Loads the data for a URL request and executes a handler block on an operation queue when the request completes or fails.
+ (void)sendAsynchronousRequest:(NSURLRequest *)request queue:(NSOperationQueue *)queue completionHandler:(void (^)(NSURLResponse*,NSData*, NSError*))handler
Parameters of [NSURLConnection sendAsynchronousRequest]
- request
- The URL request to load. The request object is deep-copied as part of the initialization process. Changes made to request after this method returns do not affect the request that is used for the loading process.[NSURLConnection sendAsynchronousRequest]
- queue
- The operation queue to which the handler block is dispatched when the request completes or failed.
- handler
- The handler block to execute.
Discussion of [NSURLConnection sendAsynchronousRequest]
If the request completes successfully, the data parameter of the handler block contains the resource data, and the error parameter is
nil. If the request fails, the data parameter is nil and the error parameter contain information about the failure.
Example of [NSURLConnection sendAsynchronousRequest]
NSURL *url = [NSURL URLWithString:urlString];
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if ([data length] > 0 && error == nil)
[delegate receivedData:data];
else if ([data length] == 0 && error == nil)
[delegate emptyReply];
else if (error != nil && error.code == ERROR_CODE_TIMEOUT)
[delegate timedOut];
else if (error != nil)
[delegate downloadError:error];
}];
Example of [NSURLConnection sendAsynchronousRequest]
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];