Synchronous and Asynchronous Request Processing

Synchronous Request Handling:

responseData = [[NSMutableData data] retain];

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://localhost/json"]];

NSURLResponse *response = nil;

NSError *error = nil;

//getting the data

NSData *newData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

//json parse

NSString *responseString = [[NSString alloc] initWithData:newData encoding:NSUTF8StringEncoding];

NSDictionary *jsonObject = [responseString JSONValue];

//Accessing JSON content

NSLog(@"type :  %@", [jsonObject objectForKey:@"Type"] );

Some explanations :

- response is the url response for the json call

- error is error returned by NSURLConnection

- newData is data returned by the server

Notice that you can cast the JSON deserialized data into a NSDictionnary or anNSMutuableArray.

Asynchronous Request Handling:

To make an Asynchronous call we’ll need to use NSURLConnection withinitWithRequest method, then we need to implement differents other methods to handle the finish of data loading, error handling etc.

//in the viewDidLoad

responseData = [[NSMutableData data] retain];

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://localhost/json"]];//asynchronous call

[[NSURLConnection alloc] initWithRequest:request delegate:self];

Implementing delegate methods :

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

[responseData setLength:0];

}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

[responseData appendData:data];

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

NSLog(@"%@", error);

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];

[responseData release];

NSDictionary *jsonObject = [responseString JSONValue];

NSLog(@"type :  %@", [jsonObject objectForKey:@"Type"] );

[connection release];

}