an example of request chaining using NSURLSession Callback

chainingRequestCallback.swift

// 1. login post request
NSURLSession.sharedSession().dataTaskWithRequest(loginRequest){ data , res , err in
    // let token = data...
    // we have token.
    let getCurrentUserURL = NSURL(string: getUserDataURL + "?token=\(token)")!
    
    // 2. get current user data
    NSURLSession.sharedSession().dataTaskWithURL(getCurrentUserURL){ data , res , err in
        
        // we have user data, and we get currentUserID
        let _getAddressesesURL = NSURL(string: getAddressesURL + "?token=\(token)&userId=\(currentUserID)")!
        
        // 3. get last friend user data
        NSURLSession.sharedSession().dataTaskWithURL(_getAddressesesURL){ data , res , err in
            
            // we have addresses. we're done
            println("done")
            
        }.resume()
    }.resume()
}.resume()