call back code challenge

Question

//Why doesn't it work

import Foundation

// Add your code below

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

// Step 2 fully completed looks like this

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, completionHandler : { (data : NSData!, reponse : NSURLResponse!, error : NSError!) -> Void in return fetchTreehouseBlogPosts(data,response,error)

}) // Add code above

dataTask.resume()

Callbacks.swift

import Foundation

// Add your code below

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


// Step 2 fully completed looks like this

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, completionHandler : {
(data : NSData!, reponse : NSURLResponse!, error : NSError!) -> Void in
return fetchTreehouseBlogPosts(data,response,error)

})
// Add code above

dataTask.resume()

Answer 1 · 2016-02-05T07:54:26Z

February 5, 2016 7:54am

Hey Muzhi Ou,

You're close! This was a difficult one for me. We have to make some changes to your completion handler. First off, when the last argument in a function is a closure, we can implement it as a trailing closure. It's much cleaner to write it this way, so I will use a trailing closure in my example below.

import Foundation

// Add your code below
typealias BlogPostCompletion = ((NSData!, NSURLResponse!, NSError!) -> Void)

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) {
    (let data, let response, let error) in
    completion(data, response, error)
}

dataTask.resume()

}

// Add code above

/* The changes I made were:
1. I used a trailing closure, writing the closure outside the parentheses
2. You don't need to specify the parameter types, just the names
3. You call the completion handler with the completion parameter name,
not the fetchTreehouseBlogPost function
4. Your fetchTreehouseBlogPost function and your completion handler return void,
so no return statement is needed
5. I used a typealias for the completion handler's function signature
*/

Good Luck!

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Muzhi Ou

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call back code challenge

1 Answer

Steven Deutsch

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Muzhi Ou

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