Cancel request if new request is made

Question

I want to implement a search functionality one of my iOS application. I have implemented UISearchBar delegates.

Now when user starts searching it makes a service API call.

For example user types:

1. A
2. Ap
3. App
4. Appl
5. Apple

So total 5 service call is made in very short time. Now i want to cancel all the service call made from 1 to 4 and I want to consider the 5th one as my final result.

I googled for the same and found that I should use NSOperationQueue and cancel the operation when not needed. Following is the code I am using for that same:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText {
    if (searchText.length > 0) {
        [self filterContentForSearchText:searchText];
    }
}

- (void)filterContentForSearchText:(NSString*)searchText {

    if ([session isInternetAvailable:NO]) {
            if (!downloadQ) downloadQ = [[NSOperationQueue alloc] init];
            if (downloadQ) {
                [downloadQ cancelAllOperations];
                NSLog(@"**********cancelAllOperations**********: %@",downloadQ.name);
            }
            downloadQ.name = searchText;
        
            NSString *strURL = [NSString stringWithFormat:@"http://192.168.1.192:8080/api/user/find/%@/",searchText];
            NSURL *url = [NSURL URLWithString:[strURL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
            NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url
                                                                  cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData
                                                              timeoutInterval:30];
        
            [urlRequest setHTTPMethod:@"GET"];
            [urlRequest setValue:@"application/json" forHTTPHeaderField:@"Accept"];
            [urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
        
            [NSURLConnection sendAsynchronousRequest:urlRequest
                                           queue:downloadQ
                               completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
                                   NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
                                   NSLog(@"===> %@",result);
                               }];
    }
}

I need help on this query. Can any one provide me some solution how can i achieve or what would be the best way to implement searching function in iOS app.

Edit With NSURLSEssion

I tried with following code and how i get the response is different sequence.

NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
defaultConfigObject.requestCachePolicy = NSURLRequestUseProtocolCachePolicy;
NSURLSession *delegateFreeSession = [NSURLSession sessionWithConfiguration:defaultConfigObject
                                                                  delegate:nil
                                                             delegateQueue:[NSOperationQueue mainQueue]];

NSString *strURL = [NSString stringWithFormat:@"%@/user/find/%@/",LIVE_SERVICE_HOST_URL,searchText];
NSURL *dataURL = [NSURL URLWithString:strURL];
NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:dataURL];
[urlRequest setHTTPMethod:@"GET"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];

[[delegateFreeSession dataTaskWithRequest:urlRequest
                        completionHandler:^(NSData *data, NSURLResponse *response,
                                            NSError *error){
        NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@===> %@",searchText,result);
}] resume];

Response come in different sequence:

1st response for A
2nd response for Appl
3rd response for Ap
4th response for Apple
5th response for App

So what can I do to over come this behaviour?

Answer 1

Alternate solution:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText {
    if ([searchText length] <= 0) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(filterContentForSearchText) object:self];
        [self performSelector:@selector(filterContentForSearchText) withObject:self afterDelay:0.5];
    }
}

Reference From: Here