NSURLConnection and pointer types bug - objective-c

Question

Here the problem, i'am using a http request, but when i use NSURLConnection to get my xml file and set a NSString *xml variable with that xml file i get a block pointer error if i return it. But if i take NSString *xml and send it to a method it tells me nothing and the xml variable is well set. Also if i return at the end of my method the variable, i get a nil at the parent calling method. How can i fix this because the return of the variable is needed. Thanks for any help, and here is my code :
The error :
incompatible block pointer types sending 'NSString *(^)NSURLResponse *, NSData *, NSError *)'to parameter of type 'void(^)(NSURLResponse *,NSData *, NSError *)'
- (NSString *)restTestRequester: (NSString *)uriRequested serviceUri:(NSString *)sUri parameters:(NSString *)uriParameters technique:(NSString *)requestTechnique {
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
NSString *l_api_key = [prefs stringForKey:#"globalPublicK"];
NSString *l_secret_key = [prefs stringForKey:#"globalSecretK"];
l_uri = [NSString stringWithFormat:#"%#/%#", uriRequested, sUri];
NSMutableURLRequest *theRequest=[NSMutableURLRequest requestWithURL:[NSURL URLWithString:l_uri]
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:60.0];
[theRequest setHTTPMethod:requestTechnique];
[theRequest setValue:#"application/xml" forHTTPHeaderField:#"Accept"];
[theRequest setValue:#"application/x-www-form-unrlencoded" forHTTPHeaderField: #"Content-Type"];
[theRequest setValue:l_api_key forHTTPHeaderField: #"EMApikey"];
[theRequest setValue:[self hmacsha1:l_uri secret:l_secret_key] forHTTPHeaderField: #"EMRequestHash"];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if( theConnection )
{
[NSURLConnection sendAsynchronousRequest:theRequest
queue:[NSOperationQueue mainQueue]
incompatible block pointer types error--> completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
here ---->xml = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]
autorelease];
works--->[self myMethod:xml];
doesn't work---> return(xml);
}
];
}
else
{
NSLog(#"theConnection is NULL");
}
[theConnection release];
equals nil variable returned-->return xml;
}

Answer 1

I think that the problem is in async call, U still don't have anything in xml when U trie to return it, your method returns before sendAsynchronousRequest finishes.
USE:
NSData* data=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSString* xml = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
It will wait until U get the result back.

Answer 2

You have several major problems. For starters, your block executes after your connection finishes. The code after the block executes after the connection STARTS. This means you releasing the connection before it finishes.
Additionally, you are creating NSURLConnection *theConnection, but never using it. When you call -sendAsynchronousRequest:queue:completionHandler: it creates a completely new handler.
The specific error you are getting is because you cannot return a value from the block. The fact that you are trying indicates that you do not have a full grasp of exactly what is happening. There are many good references around the Internet about blocks and asynchronous programming. I suggest you find one.
NSURL *targetURL = [NSURL URLWithString:l_uri];
NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:targetUrl
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:60.0];
[theRequest setHTTPMethod:requestTechnique];
[theRequest setValue:#"application/xml" forHTTPHeaderField:#"Accept"];
[theRequest setValue:#"application/x-www-form-unrlencoded" forHTTPHeaderField: #"Content-Type"];
[theRequest setValue:l_api_key forHTTPHeaderField: #"EMApikey"];
[theRequest setValue:[self hmacsha1:l_uri secret:l_secret_key] forHTTPHeaderField: #"EMRequestHash"];
[NSURLConnection sendAsynchronousRequest:theRequest
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
// Here the connection is complete and the data is usable.
NSString *xml = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
[self myMethod:xml];
[xml release];
}];
// Here the Connection has only been queued and no data is available.