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

Posted by Rezwanul Kabir
Rezwanul Kabir
3,136 Points

Why the following code is not accepted as valid?

I Code Challage "callback-methods-with-closures" I am posting the following answer:

typealias BlogPostCompletion = (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void

func fetchTreehouseBlogPosts (completion : BlogPostCompletion) { }

It is asking me to make sure that the method name is fetchTreehouseBlogPosts and to check that the syntax is right. I don't understand where the code is wrong! I have checked it in a playground and works fine without any syntax error

Callbacks.swift 
import Foundation

// Add your code below

typealias BlogPostCompletion = (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void

func fetchTreehouseBlogPosts (completion : BlogPostCompletion) {
}

2 Answers

Richard Lu
Richard Lu
20,185 Points
Richard Lu
Richard Lu
20,185 Points

I remember this challenge and I changed the return type for the signature to '()' instead of void. This worked for me. You are absolutely correct, but I think it's just a preference that treehouse has.

typealias BlogPostCompletion = (NSData!, NSURLResponse!, NSError!) -> ()
Rezwanul Kabir
Rezwanul Kabir
3,136 Points

No, it still isn't working! pretty strange!!

Roberta Voulon
Roberta Voulon
5,792 Points
Roberta Voulon
Roberta Voulon
5,792 Points

I think a ton of people are stuck on this, I finally got a hint from somewhere and it worked for me, so I'm re-posting this where I can: What made it work for me in the end was wrap the signature in outer parenthesis like this:

typealias BlogPostCompletion = ((NSData!, NSURLResponse!, NSError!) -> Void)
func fetchTreehouseBlogPosts(completion: BlogPostCompletion) {}

You shouldn't have to do this though! It's perfectly valid without the wrapping parentheses.

Rezwanul Kabir
Rezwanul Kabir
3,136 Points

Yes, that did the trick for me as well! Got the hint from another post. :)