Asynchronous Connection Download Callback - ios

Question

I created a class customDownload with the following methods:
-(NSString *) getTextFromLink: (PreliteRequest *) requestDetails
asyncConnection: (BOOL) isAsync
callbackMethod: (SEL) methodToExecute {
mainRequest = requestDetails;
NSMutableURLRequest *postRequest = [[NSMutableURLRequest alloc] init];
NSURLRequest *getRequest = [[NSURLRequest alloc] init];
NSURLConnection *connection;
NSURLResponse * response = nil;
NSError * error = nil;
if ([[requestDetails getType] isEqualToString:#"POST"]) {
[postRequest setURL:[NSURL URLWithString:[requestDetails getUrl]]];
[postRequest setHTTPMethod:[requestDetails getType]];
[postRequest setValue:[requestDetails getPostLenght] forHTTPHeaderField:#"Content-Length"];
[postRequest setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[postRequest setHTTPBody:[requestDetails getPostParameters]];
if (isAsync) {
tmpMethod = methodToExecute;
connection = [[NSURLConnection alloc] initWithRequest:postRequest delegate:self];
} else
downloadedData = (NSMutableData *)[NSURLConnection sendSynchronousRequest:postRequest returningResponse:&response error:&error];
} else {
getRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#%#",[requestDetails getUrl],[requestDetails getGetParameters]]]];
if (isAsync) {
tmpMethod = methodToExecute;
connection = [[NSURLConnection alloc] initWithRequest:getRequest delegate:self];
} else
downloadedData = (NSMutableData *)[NSURLConnection sendSynchronousRequest:getRequest returningResponse:&response error:&error];
}
NSString *result=[[NSString alloc]initWithData:downloadedData encoding:NSUTF8StringEncoding];
return result;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
downloadedData = [[NSMutableData alloc] init];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append the new data to the instance variable you declared
[downloadedData appendData:data];
}
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
willCacheResponse:(NSCachedURLResponse*)cachedResponse {
return nil;
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSString *tmpResult = [[NSString alloc]initWithData:downloadedData encoding:NSUTF8StringEncoding];
[self performSelector:tmpMethod withObject:tmpResult];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSLog(#"Connection error: %#",error);
}
In my view controller I declare the previous class and call the only method of that class getTextFromLink.
download = [[customDownload alloc] init];
[download getTextFromLink:request asyncConnection:YES callbackMethod:tmpSelector];
SEL tmpSelector = #selector(printResult:);
-(void) printResult:(NSString *) resultToPrint {
NSLog(#"Risultato: %#",resultToPrint);
}
I pass to getTextFromLink the tmpSelector as parameter because that is the method I would like to call as soon the getTextFromDownloadLink has finished its job.
Actually getTextFromLink execute an asynchronous connection.
What I'm trying to do is to execute something when the asyncronous connection finished to download datas.
I would like to create a callback custom class to do this.
Can anyone help me?

Answer 1

Rather than this selector model, generally people would use blocks for this. For example, define a typedef for your block:
typedef void(^PreliteRequestCompletionHandler)(NSString *string);
Since you're dealing with an asynchronous pattern, you might want to define a property which you can use to save this completion handler to call later:
#property (nonatomic, copy) PreliteRequestCompletionHandler completionHandler;
You can then change that selector parameter to be a block parameter:
-(NSString *) getTextFromLink: (PreliteRequest *) requestDetails
asyncConnection: (BOOL) isAsync
completionHandler: (PreliteRequestCompletionHandler)completionHandler {
self.completionHandler = completionHandler;
// do stuff
}
And then, when you want to call that completion block, you do something like:
NSString *result = ...;
if (self.completionHandler) {
self.completionHandler(result);
}
And then you can now use this new block parameter to your method:
download = [[customDownload alloc] init];
[download getTextFromLink:request asyncConnection:YES completionHandler:^(NSString *result) {
NSLog(#"Risultato: %#", result);
}];