Using sendAsynchronousRequest:queue:completionHandler: for URL request

Question

I'm working on an update of an iOS app that another developer created. He was using ASIHTTPRequest to handle http requests. However, the version of the app I have to work with crashes. Since ASIHTTPRequest is not being updated anymore, I thought then that I should switch to using AFNetworking, but it's far too complicated for me to figure out.

So finally I thought I could just use NSURLConnection on its own.

Here is the original code that I'm trying to replace:

-(NSArray*)readUTF16LEFeed:(NSURL*) urlToRead{
    ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:urlToRead];
    [request startSynchronous];
    NSError *error = [request error];
    if (!error) {
        lastModified = [NSDate date];
        NSData *response = [request responseData];//UTF-16LE
        NSString* responseString = [[NSString alloc] initWithData:response encoding:NSUTF16LittleEndianStringEncoding];
        DLog(@"string is: %@",responseString);
        responseString = [responseString stringByReplacingOccurrencesOfString:@"ISO-8859-1" withString:@"UTF16-LE"];
        NSData* data = [responseString dataUsingEncoding:NSUTF16LittleEndianStringEncoding];
        return [self parseNamesFromXML:data];
    }
    return nil;
}

And here is what I'm trying to use instead:

-(NSArray*)readUTF16LEFeed:(NSURL*) urlToRead{

    NSURLRequest *request = [NSURLRequest requestWithURL:urlToRead];
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[NSOperationQueue mainQueue]
                           completionHandler:^(NSURLResponse *response, NSData *data, NSError *error ) {

                               if ([data length] >0 && error == nil)
                               {
                                   // DO YOUR WORK HERE
                                   lastModified = [NSDate date];

                                   //   NSData *response = [request responseData];//UTF-16LE
                                   NSString* responseString = [[NSString alloc] initWithData:data encoding: NSUTF16LittleEndianStringEncoding];
                                   DLog(@"string is: %@",responseString);
                                   responseString = [responseString stringByReplacingOccurrencesOfString:@"ISO-8859-1" withString:@"UTF16-LE"];
                                   NSData* data = [responseString dataUsingEncoding:NSUTF16LittleEndianStringEncoding];
                                   return [self parseNamesFromXML:data];
                               }

                               else if ([data length] == 0 && error == nil)
                               {
                                   NSLog(@"Nothing was downloaded.");
                               }
                               else if (error != nil){
                                   NSLog(@"Error = %@", error);
                               }
                           }];
    return nil;
}

However, I'm getting the error "Incompatible block pointer types sending NSArray to parameter of type void. And also "Control may reach end of non-void block."

How can I get this to work?

Answer 1

Make return type of your method as void. Dont return anything. Just call [self parseNamesFromXML:data]; method.

-(void)readUTF16LEFeed:(NSURL*) urlToRead{


NSURLRequest *request = [NSURLRequest requestWithURL:urlToRead];
[NSURLConnection sendAsynchronousRequest:request
                                   queue:[NSOperationQueue mainQueue]
                       completionHandler:^(NSURLResponse *response, NSData *data, NSError *error ) {

                       if ([data length] >0 && error == nil)
                       {

                           // DO YOUR WORK HERE
                           lastModified = [NSDate date];

                      //   NSData *response = [request responseData];//UTF-16LE
                           NSString* responseString = [[NSString alloc] initWithData:data encoding: NSUTF16LittleEndianStringEncoding];
                           DLog(@"string is: %@",responseString);
                           responseString = [responseString stringByReplacingOccurrencesOfString:@"ISO-8859-1" withString:@"UTF16-LE"];
                           NSData* data = [responseString dataUsingEncoding:NSUTF16LittleEndianStringEncoding];
                           [self parseNamesFromXML:data];
                       }


                       else if ([data length] == 0 && error == nil)
                       {
                           NSLog(@"Nothing was downloaded.");
                       }
                       else if (error != nil){
                           NSLog(@"Error = %@", error);
                       }

                   }];
}

In parseNamesFromXML method, process your results and assign results array to a property. You can access it where ever you want.

-(void) parseNamesFromXML:(NSData *)xmlData
{     
    NSError *error;          
    //DLog(@"data is %@", [[NSString alloc] initWithData:xmlData encoding:NSUTF8StringEncoding ]);     

    GDataXMLDocument *doc = [[GDataXMLDocument alloc] initWithData:xmlData                                                            options:0 error:&error];          

    if (doc)
    {         
        self.dataArray = [self parseXmlDoc:doc]; 
    }              
}

Answer 2

The completion block is called asynchronously, so by the time your code reaches return [self parseNamesFromXML:data]; the methods scope is already done (meaning the method returned nil.

Try using [NSURLConnection sendSynchronousRequest:returningResponse:error:] instead, since the original code is also synchronous.

Edit: As Julian Król suggested, if you return something within a block, it will be counted as the return value of this block, not of the original method. But since the block does not have a return value, you'll get the compiler error.