[Solved] how can I use NSURLConnection Asynchronously?

Question

Block code is your friend. I have created a class which does this for you

Objective-C Block code. Create this class here

Interface class

#import <Foundation/Foundation.h>
#import "WebCall.h"

@interface WebCall : NSObject
{
    void(^webCallDidFinish)(NSString *response);

}

@property (nonatomic, retain) NSMutableData *responseData;

-(void)setWebCallDidFinish:(void (^)(NSString *))wcdf;

-(void)webServiceCall :(NSString *)sURL_p : (NSMutableArray *)valueList_p : (NSMutableArray *)keyList_p;

@end

Implementation class

#import "WebCall.h"
#import "AppDelegate.h"
@implementation WebCall

@synthesize responseData;

-(void)setWebCallDidFinish:(void (^)(NSString *))wcdf
{
    webCallDidFinish = [wcdf copy];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;
    int responseStatusCode = [httpResponse statusCode];

    NSLog(@"Response Code = %i", responseStatusCode);
    if(responseStatusCode < 200 || responseStatusCode > 300)
    {
        webCallDidFinish(@"failure");
    }



    [responseData setLength:0];
}

- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace
{

    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
    [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];

    [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [responseData appendData:data]; 
}

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

    NSLog(@"WebCall Error: %@", error);
    webCallDidFinish(@"failure");
}

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

        NSString *response = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
        response = [response stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        webCallDidFinish(response);

}

-(void)webServiceCall :(NSString *)sURL_p : (NSMutableArray *)valueList_p : (NSMutableArray *)keyList_p
{
    NSMutableString *sPost = [[NSMutableString alloc] init];

    //If any variables need passed in - append them to the POST
    //E.g. if keyList object is username and valueList object is adam will append like
    //http://test.jsp?username=adam
    if([valueList_p count] > 0)
    {
        for(int i = 0; i < [valueList_p count]; i++)
        {
            if(i == 0)
            {
                    [sPost appendFormat:@"%@=%@", [valueList_p objectAtIndex:i],[keyList_p objectAtIndex:i]];
            }
            else
            {

                    [sPost appendFormat:@"&%@=%@", [valueList_p objectAtIndex:i], [keyList_p objectAtIndex:i]];
            }
        }
    }


    NSData * postData = [sPost dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:NO];
    NSString * postLength = [NSString stringWithFormat:@"%d",[postData length]];



    NSURL * url = [NSURL URLWithString:sURL_p];
    NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:5];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPMethod:@"POST"];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:postData];

    NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];

    if (theConnection)
    {
        self.responseData = [NSMutableData data];
    }


}

@end

Then you to make this web call, you call it like this

     WebCall *webCall = [[WebCall alloc] init];


        [webCall setWebCallDidFinish:^(NSString *response){

            //This method is called as as soon as the web call is finished

NSString *trimmedString = [response stringByTrimmingCharactersInSet:
                                   [NSCharacterSet whitespaceAndNewlineCharacterSet]];
        if([trimmedString rangeOfString:@"failure"].location == NSNotFound)
        {
           //Successful web call
        }
        else
        {
           //If the webcall failed due to an error
        }

        }];


        //Make web call here
        [webCall webServiceCall:@"http://www.bbc.co.uk/" :nil :nil];

See the setWebCallDidFinish method, it will not be called until the webcall has finished.

Hope that helps!!

Accepted Answer