getting data from URL in Swift

Question

I'm trying to download JSON file from server & following an tutorial to do this (http://www.learnswiftonline.com/mini-tutorials/how-to-download-and-read-json/)

First I tried 'checking the response' part (I added some part to see what's wrong)

let requestURL: NSURL = NSURL(string: "http://www.learnswiftonline.com/Samples/subway.json")!
let urlRequest: NSMutableURLRequest = NSMutableURLRequest(URL: requestURL)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(urlRequest) {
    (data, response, error) -> Void in

        let httpResponse = response as! NSHTTPURLResponse
        let statusCode = httpResponse.statusCode

        if (statusCode == 200) {
            print("Everyone is fine, file downloaded successfully.")
        } else  {
            print("Failed")
        }

task.resume()

This should print either "Everyone is fine~" or "Failed" but neither comes up... I tried to see statusCode so I put print(statusCode) inside task but again nothing is printed.

This is my screenshot of the playground:

+

CFRunLoop in Swift Command Line Program

This was the answer I was looking for, since I was dealing with OS X command line application (I moved the whole bunch to playground to see what would happen). Check this if you're the same with me

Answer 1

You can not see anything because dataTaskWithRequest is asynchronous, and your playground just stops after 'task.resume()`. The asynchronous task does not get the change to run.

You can call this in the end, after task.resume :

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

also 'import XCPlayground', something like this:

import Foundation
import XCPlayground

let requestURL: NSURL = NSURL(string:  "http://www.learnswiftonline.com/Samples/subway.json")!
let urlRequest: NSMutableURLRequest = NSMutableURLRequest(URL: requestURL)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithRequest(urlRequest) {(data, response, error) -> Void in

  let httpResponse = response as! NSHTTPURLResponse
  let statusCode = httpResponse.statusCode

  if (statusCode == 200) {
     print("Everyone is fine, file downloaded successfully.")
  } else  {
     print("Failed")
  }

}
task.resume()

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

This post may clarify more: How do I run Asynchronous callbacks in Playground

EDIT:

In Swift 3, this changed a bit.

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true