add Authentication to AFHTTPRequestOperation

afn_authentication

//1. using completion block
[operation setAuthenticationChallengeBlock:
        ^(NSURLConnection *connection, NSURLAuthenticationChallenge *challenge) {
   NSURLCredential *cred = [NSURLCredential 
    credentialWithUser:@"username" 
    password:@"password" 
    persistence:NSURLCredentialPersistenceForSession];

   [[challenge sender] useCredential:cred forAuthenticationChallenge:challenge];
}];

//2. add to request header
NSURLMutableRequest *request = [NSURLMutableRequest
                                requestWithURL:[NSURL URLWithString:fileURL]];
NSData* authData = [[[NSString 
    stringWithFormat:@"username:password"] 
        stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding] 
            dataUsingEncoding: NSASCIIStringEncoding];
NSString *finalAuth = [authData base64EncodedString];
finalAuth = [NSString stringWithFormat:@"Basic %@",finalAuth];
[request setValue:finalAuth forHTTPHeaderField:@"Authorization"];

//3. add credentials to ops
NSURLCredential *credential = [NSURLCredential 
    credentialWithUser:@"login" 
    password:@"password" 
    persistence:NSURLCredentialPersistenceForSession];

[operation setCredential:credential];