How to make sure code is run every time viewController is viewed - ios

Question

How can I have my app run my code every time the app is viewed and not just every time it is opened? Right now I have to exit it, and open it again to run the code.
My app pulls data via JSON and displays it in labels. All of my code is in viewDidLoad.
Is the answer in putting all of the code in viewDidAppear?
Thanks in advance
Here is the whole code:
//
// ViewController.swift
// KitesurfioApp
//
// Created by Lasse Kristensen on 24/10/14.
// Copyright (c) 2014 Lasse Kristensen. All rights reserved.
//
import UIKit
import CoreData
class ViewController: UIViewController {
#IBOutlet weak var labelSpeed: UILabel!
override func viewDidLoad() {
NSNotificationCenter.defaultCenter().addObserver(self, selector: "backgroundNotification:", name: UIApplicationWillEnterForegroundNotification, object: nil);
// Set logo in nav bar
navigationItem.titleView = UIImageView(image: UIImage(named: "logo"))
refresh();
}
func backgroundNotification(noftification:NSNotification){
refresh();
println("Refreshed after background")
}
func refresh() {
// Global save values
var appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
var context: NSManagedObjectContext = appDel.managedObjectContext!
// JSON Fetching
let urlPath = "http://api.openweathermap.org/data/2.5/weather?lat=55.564120&lon=12.568605"
let url = NSURL(string: urlPath)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!, completionHandler: {data, response, error -> Void in
dispatch_async(dispatch_get_main_queue(),{
if (error != nil) {
println(error)
}
else {
// Delete old entries in CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
for result in results! {
context.deleteObject(result as NSManagedObject)
context.save(nil)
}
// Start fetching JSON
let jsonResult = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary
var item = jsonResult["wind"] as NSDictionary
var degrees:Float = item["deg"] as Float
var speed:Float = item["speed"] as Float
// Start saving JSON
var newItem = NSEntityDescription.insertNewObjectForEntityForName("WindData", inManagedObjectContext: context) as NSManagedObject
var speedValue:Float = speed as Float
var degreesValue:Float = degrees as Float
newItem.setValue(speedValue, forKey: "speed")
newItem.setValue(degreesValue, forKey: "degrees")
context.save(nil)
}
// Start fetching from CoreData
var request = NSFetchRequest(entityName: "WindData")
request.returnsObjectsAsFaults = false
var results = context.executeFetchRequest(request, error: nil)
if results!.count > 0 {
for result in results as [NSManagedObject] {
let degrees:Float = result.valueForKey("degrees")! as Float
let speed:Float = result.valueForKey("speed")! as Float
if speed > 6.0 {
self.labelSpeed.text = "Go kitesurf: \(speed) m/s \(degrees)"
}
else {
self.labelSpeed.text = "Stay in: \(speed) m/s \(degrees)"
}
}
}
else {
println("No data")
}
});
})
task.resume()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

You need to add UIApplicationWillEnterForegroundNotification and refresh your screen there.Put all code from viewDidLoad to helper function like refreh and call it when viewDidLoad or you come in foreground from background or whenever you want to refresh screen.
override func viewDidLoad() {
NSNotificationCenter.defaultCenter().addObserver(self, selector: "backgoundNofification:", name: UIApplicationWillEnterForegroundNotification, object: nil);
//put all code of your viewDidLoad to refresh
refresh();
}
func backgoundNofification(noftification:NSNotification){
refresh();
}
func refresh() {
//here is your all code to fetch data and all
}