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iOS Build a Weather App with Swift Managing Complexity Callback Methods With Closures

Posted by Justin Doo
Justin Doo
3,607 Points

Having problem with part 2 of the call back/ closure Swift weather app challenge, can anyone help?

Been trying to figure this out for the las few days, I'm stumped. Any help will be appreciated.

Callbacks.swift 
import Foundation

typealias BlogPostCompletion = ((NSData!, NSURLResponse!, NSError!) -> Void)
// Add your code below
func fetchTreehouseBlogPosts (completion: BlogPostCompletion) {

let blogURL = NSURL(string: "http://blog.teamtreehouse.com/api/")
  let requestURL = NSURL(string: "get_recent_summary/?count=20", relativeToURL: blogURL)

  let request = NSURLRequest(URL: requestURL!)

  let config = NSURLSessionConfiguration.defaultSessionConfiguration()
  let session = NSURLSession(configuration: config)

  // Add your code between the comments
let dataTask: NSURLSessionDataTask = session.dataTaskWithRequest(request)
    {(data, response, error) in 
    return (completion: data, response, error)}
  // Add code above
dataTask.resume()
}

1 Answer

Rasmus Rønholt
Rasmus Rønholt
Courses Plus Student 17,358 Points

Hey Justin If you didn't already solve this, then here goes :)

The completionHandler of dataTaskWithRequest should return Void, but in your closure you are trying to "return" the completion. In stead you should simply call the handler that is passed to the fetchTreehouseBlogPosts method.

let dataTask = session.dataTaskWithRequest(request) {
    (let data, let response, let error) in
    // Do stuff here
    completion(data, response, error)
}

Now the above is completely valid, but if you are not doing anything with the results, you might as well just point to the completion handler that is passed to the fetchTreehouseBlogPosts method like so:

let dataTask = session.dataTaskWithRequest(request, completionHandler: completion)
Kevin Scully
Kevin Scully
6,506 Points
Kevin Scully
Kevin Scully
6,506 Points

In the challenge, it seems the more concise second option doesn't work.

Rasmus Rønholt
Rasmus Rønholt
Courses Plus Student 17,358 Points

Nope - seems you're right Kevin... It does work in the real world, though.