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iOS

Woongshik Choi
Woongshik Choi
42,387 Points
Posted by Woongshik Choi
Woongshik Choi
42,387 Points

What's wrong on this syntax in Swift?

I am not sure what's wrong on this syntax...

import Foundation

// Add your code below func fetchTreehouseBlogPosts(completionHandler: {(data: NSData!, response: NSResponse!, error: NSError!) -> Void in })

7 Answers

Grant Powell
Grant Powell
2,356 Points

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

Matthew Young
Matthew Young
5,133 Points
Matthew Young
Matthew Young
5,133 Points

The first snippet of code that Brian posted doesn't work because of the curly braces in it. Remove them and the code works fine.

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

tate
tate
13,435 Points
tate
tate
13,435 Points

You haven't really explained much but I'm guessing that the thing wrong is the fact that half of your code is commented out.

Woongshik Choi
Woongshik Choi
42,387 Points
Woongshik Choi
Woongshik Choi
42,387 Points

That's my mistake.

I am doing a challenge below...

We're writing an app to fetch the most recent blog posts from the Treehouse blog. This requires making a network request using asynchronous methods that execute in the background. For that we need a closure. Create a method called fetchTreehouseBlogPosts, that has a single parameter - a completion handler. The closure has three parameters: a data object containing the results of the request as type NSData!, the HTTP response object from our request as type NSURLResponse!, an error object as type NSError!, and a return type of void.

Note: If you prefer to use a typealias to make the method signature clear, name it BlogPostCompletion

And my code is...

import Foundation

// Add your code below

func fetchTreehouseBlogPosts(completionHandler: {(data: NSData!, response: NSResponse!, error: NSError!) -> Void in })

So I am not sure what's wrong on my code...

Grant Powell
Grant Powell
2,356 Points
Grant Powell
Grant Powell
2,356 Points

I copied and pasted that code and still get an error.

Grant Powell
Grant Powell
2,356 Points
Grant Powell
Grant Powell
2,356 Points

It seems there is some mistake...

1) This code does NOT work: func fetchTreehouseBlogPosts(completion: {((NSData!, NSResponse!, NSError!) -> Void)})

2) Nor does this: func fetchTreehouseBlogPosts(completion: ((NSData!, NSURLResponse!, NSError!) -> Void)) {}

3) However, this DOES work: typealias BlogPostCompletion = ((NSData!, NSURLResponse!, NSError!) -> Void) func fetchTreehouseBlogPosts (completion: BlogPostCompletion) { }

It seems to me that #2 should also work. Am I misunderstanding the syntax?

Adam Creasey
Adam Creasey
5,756 Points
Adam Creasey
Adam Creasey
5,756 Points 
func fetchTreehouseBlogPosts(completion: ((NSData!, NSURLResponse!, NSError!) -> Void)){}

Not sure how you guys went, but this worked for me

Seth Rininger
Seth Rininger
586 Points
Seth Rininger
Seth Rininger
586 Points

(NSData!, NSURLResponse!, NSError!) -> Void..... you have to have parentheses around the whole thing like ((NSData!, NSURLResponse!, NSError!) -> Void) instead of my first one.