I am trying to use CKSubscription to subscribe to changes. I am following Apple's docs which seems to be very general and incomplete.
Link to Apple Doc
I have got the point of getting Record ID sent to my app via the didReceiveRemoteNotification method in AppDelegate and I have got my Record Id: using this code:
func application(application: NSApplication, didReceiveRemoteNotification userInfo: [String : AnyObject]) {
let cknNotification = CKNotification(fromRemoteNotificationDictionary: userInfo as! [String:NSObject])
if cknNotification.notificationType == .Query,
let queryNotification = cknNotification as? CKQueryNotification {
let recordId = queryNotification.recordID
print(recordId)
}
How do I convert the CKNotification into the Actual Object I stores in Cloudkit? Do I need to perform another fetch or is the data contained in the CKNotification that I just need to Cast.
Looks like I worked it out.
The Notification only lets you know that they have changed. You need to do the work to pull the new records and update them. ( Makes sense really)
privateCloudDatabase().fetchRecordWithID(recordId!, completionHandler: { (recordfetched, error) in
//Check the Record Type if multiple.. I only have one type.
let myRecordType = recordfetched?.recordType
let myObject = mySuperObject(record: recordfetched!)
print("done")
})
// I should probably add more optional checking - but above just illustrates the solution and how simple it is to get.
Related
My Swift 3, Xcode 8.2 MacOS app loads several tables through web services calls. Since the tables are used by one or more of my seven view controllers, I placed them in the AppDelegate.
The problem is that the AppDelegate methods applicationWillFinishLaunching and applicationDidFinishLaunching run after the ViewController viewDidLoad methods.
As a result the table views show no data. I was able to get it to work correctly by calling the appDelegate method that loads the data from one of the ViewController viewDidLoad methods. Since any of the ViewControllers could be invoked on application start up, I would have to add the call to all of them and some sort of flagging method to prevent redundant loads.
My question is: where can I place code that will execute prior to the ViewControllers loading? The code loads data into multiple arrays of dictionary. These arrays are in the AppDelegate.
I read up on #NSApplicationMain and replacing it with a main.swift. I assume none of application objects would have been instantiated at that point so I couldn't call their methods and don't think my code would be valid outside of a class.
The pertinent part of my appDelegate:
class AppDelegate: NSObject, NSApplicationDelegate {
var artists: [[String:Any]]? = nil
var dispatchGroup = DispatchGroup() // Create a dispatch group
func getDataFromCatBox(rest: String, loadFunction: #escaping ([[String: Any]]?) -> Void) {
let domain = "http://catbox.loc/"
let url = domain + rest
var request = URLRequest(url: URL(string: url)!)
request.httpMethod = "Get"
let session = URLSession.shared
var json: [[String:Any]]? = nil
dispatchGroup.enter()
session.dataTask(with: request) { data, response, err in
if err != nil {
print(err!.localizedDescription)
return
}
do {
json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? [[String: Any]]
}
catch {
print(error)
}
loadFunction(json)
self.dispatchGroup.leave()
}.resume()
}
func loadArtistTable(array: [[String: Any]]?) {
artists = array
}
}
The ViewController code:
override func viewDidLoad() {
super.viewDidLoad()
appDelegate = NSApplication.shared().delegate as! AppDelegate
appDelegate.getDataFromCatBox(rest: "artists.json", loadFunction: appDelegate.loadArtistTable)
appDelegate.dispatchGroup.wait()
artistTable.reloadData()
}
The code works in that the TableView is populated when the window appears. While it's not a lot of code, I would have to duplicate across all my View Controllers.
This a prototype. The production version will have 14 tables and invocations.
I guess my comment should be an answer. So. Why not just make the window containing the table views not be visible on launch? Then in didFinishLaunching, load the table data and then show the window.
I don't think there is any way to do what I want the way it is structured in the question. The ViewController code could be reduced to
appDelegate = NSApplication.shared().delegate as! AppDelegate
appDelegate.getDataFromCatBox(rest: "artists.json", loadFunction: appDelegate.loadArtistTable
by creating a wrapper function in AppDelegate that had the wait in it. It also could contain a flag that indicated that a given table had already been loaded so as not to make a redundant call.
I ended up going with a different approach: I created a super class with singleton subclasses for each table. Now my viewDidLoad method looks like this:
artists.loadTable() // The sublass
artistTable.reloadData()
If any one comes up with a cleaner solution to the original problem, I'll accept their answer in place of mine.
I have the following function:
override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
let pasteboard = sender.draggingPasteboard()
let fileURL = URL(from: pasteboard)
// Does something
}
I am getting the following error at "URL(from: pasteboard)"
Argument labels '(from:)' do not match any available overloads
From what I can tell NSURL has the following method.
init?(from pasteBoard: NSPasteboard)
I don't know what I am doing wrong?
Short answer is URL is not the same as NSURL. The changes to Swift 3 didn't just remove the NS, to make things easier to read, but implemented there own simplistic version of NSURL. When on an Apple device it will secretly use NSURL.
To fix it I changed my code to use this:
let fileURL = NSURL(from: pasteboard) as? URL
More information about the removal of NS can be found here: https://github.com/apple/swift-evolution/blob/master/proposals/0086-drop-foundation-ns.md
If you want to view the source code it is found here: https://github.com/apple/swift/blob/master/stdlib/public/SDK/Foundation/URL.swift
I think I am tired of NSCache(). Could not understand what's the problem behind this. Trying to save an array of [AnyObject] to NSCahce(), which I have done using this following line of code.
NSCache().setObject(data, forKey: "News")
And tried to get it back using this way.
if let news = NSCache()("News") as? [AnyObject]
{
}
else
{
// I am always here :)
}
So I was thinking what's the problem with this. After searching a bit in Google I could see that setting totalCostLimit and countLimit will help you solve this problem. So I have set it like this.
NSCache().totalCostLimit = 50000
NSCache().countLimit = 50000
After setting this also, it was not working. So I thought of running this code in main thread, which I have done like this.
dispatch_async(dispatch_get_main_queue()) {
NSCache().setObject(data, forKey: "News")
}
Still it returned nil. Now last but not the least I have created one global instance of NSCache() and called all these operations using that instance. Well, doing like that also didn't give the expected result. It always gave me nil.
What's happening here? I know that NSCache() can store AnyObject values. I am saving lot of images in the same project without any problem, when I am trying to save this it returns nil.
Well this AnyObject contains some custom classes. Is that can be a problem? If yes, how will I save it locally without using CoreData or NSUserdefaults.
How I created an instance globally and accessed these. Created one instance of NSCache in the AppDelegate.swift file but outside of AppDelegate class
let mainCache = NSCache()
#NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
func applicationDidFinishLaunching(aNotification: NSNotification)
{
mainCache.totalCostLimit = 50000
mainCache.countLimit = 50000
}
}
Later I have used it like this.
mainCache.setObject(data, forKey: "News")
And getting the data back like this.
if let news = mainCache.objectForKey("News") as? [AnyObject]
{
}
else
{
// Always here :)
}
When you write NSCache() you are creating a new NSCache instance. You're doing this on just about every line.
What you need to do is create one instance, let myCache = NSCache(), and then reuse it: myCache.setObject(data, forKey: "News").
I'm a new, in training, swift programmer and have run into an issue with an app that I'm trying to put together.
I've searched through the forum and have found really helpful information but haven't been able to resolve my issue based on the results unfortunately.
I have an app set up to upload user images as PFFiles to parse but can't seem to have them download to the tableview in my table view controller.
A majority of the code I have tried to implement hasn't caused any errors but also hasn't downloaded the desired images.
I apologize if this is a very basic issue but I've exhausted my researching outlets.
I have the images uploading to a single class called Post and want to be able to pull images based on the current user's ID.
I've tried querying the information but always have an error returned that says that the system was unable to find anything for the query. I'm not sure if there is a better way to upload and classify the information on parse or if I'm not coding the call back correctly. I'm essentially wanting to be able to retrieve the user's uploaded images and descriptions and display them on an "Account" page.
I'm working in Xcode 7.2 in Swift 2.
So there are three things we have to care about:
1. structure of post
It would be better if you store the User in a pointer. A pointer is easier to save and retrieve. (Pointers is a way to present one to many Relations, but in our case this means One to One).
So in the data browser(parse.com) replace the column "userID" with "user" type: Pointer, target class: User.
Then in xCode
post["user"] = PFUser.currentUser()
2. Get All posts of a User
Add this code:
let query = PFQuery(className: "Post")
query.whereKey("user", equalTo: PFUser.currentUser()!)
query.getFirstObjectInBackgroundWithBlock { (obj: PFObject?, err: NSError?) -> Void in
if err != nil{
// DO something with the objets:
myArray = obj
}
}
3. Get the image
Lets say you have a ImageView like imageView
let file: PFFile = post["imageFile"] as! PFFile
file.getDataInBackgroundWithBlock { (data: NSData?, err: NSError?) -> Void in
if data != nil{
imageView.image = UIImage(data: data!)
}
}
Now you're done:)
But just a little thing to improve your code:
You don't need to dismiss the Alert after OK is pressed because if you set style to .Cancel this is automatically done! So change
alert.addAction((UIAlertAction(title: "OK", style: .Default, handler: { (action) -> Void in
self.dismissViewControllerAnimated(true, completion: nil) })))
to
alert.addAction((UIAlertAction(title: "OK", style: .Cancel, handler: nil)))
I've read Apple's Pasteboard Programming Guide, but it doesn't answer a particular question I have.
I'm trying to write a Cocoa application (for OS X, not iOS) that will keep track of everything that is written to the general pasteboard (so, whenever any application copies and pastes, but not, say, drags-and-drops, which also makes use of NSPasteboard). I could (almost) accomplish this by basically polling the general pasteboard on a background thread constantly, and checking changeCount. Of course, doing this would make me feel very dirty on the inside.
My question is, is there a way to ask the Pasteboard server to notify me through some sort of callback any time a change is made to the general pasteboard? I couldn't find anything in the NSPasteboard class reference, but I'm hoping it lurks somewhere else.
Another way I could imagine accomplishing this is if there was a way to swap out the general pasteboard implementation with a subclass of NSPasteboard that I could define myself to issue a callback. Maybe something like this is possible?
I would greatly prefer if this were possible with public, App Store-legal APIs, but if using a private API is necessary, I'll take that too.
Thanks!
Unfortunately the only available method is by polling (booo!). There are no notifications and there's nothing to observe for changed pasteboard contents. Check out Apple's ClipboardViewer sample code to see how they deal with inspecting the clipboard. Add a (hopefully not overzealous) timer to keep checking for differences and you've got a basic (if clunky) solution that should be App-Store-Friendly.
File an enhancement request at bugreporter.apple.com to request notifications or some other callback. Unfortunately it wouldn't help you until the next major OS release at the earliest but for now it's polling until we all ask them to give us something better.
There was once a post on a mailing list where the decision against a notification api was described. I can't find it right now though. The bottom line was that probably too many applications would register for that api even though they really wouldn't need to. If you then copy something the whole system goes through the new clipboard content like crazy, creating lots of work for the computer. So i don't think they'll change that behavior anytime soon. The whole NSPasteboard API is internally built around using the changeCount, too. So even your custom subclass of NSPasteboard would still have to keep polling.
If you really want to check if the pasteboard changed, just keep observing the changeCount very half second. Comparing integers is really fast so there's really no performance issue here.
Based on answer provided by Joshua I came up with similar implementation but in swift, here is the link to its gist: PasteboardWatcher.swift
Code snippet from same:
class PasteboardWatcher : NSObject {
// assigning a pasteboard object
private let pasteboard = NSPasteboard.generalPasteboard()
// to keep track of count of objects currently copied
// also helps in determining if a new object is copied
private var changeCount : Int
// used to perform polling to identify if url with desired kind is copied
private var timer: NSTimer?
// the delegate which will be notified when desired link is copied
weak var delegate: PasteboardWatcherDelegate?
// the kinds of files for which if url is copied the delegate is notified
private let fileKinds : [String]
/// initializer which should be used to initialize object of this class
/// - Parameter fileKinds: an array containing the desired file kinds
init(fileKinds: [String]) {
// assigning current pasteboard changeCount so that it can be compared later to identify changes
changeCount = pasteboard.changeCount
// assigning passed desired file kinds to respective instance variable
self.fileKinds = fileKinds
super.init()
}
/// starts polling to identify if url with desired kind is copied
/// - Note: uses an NSTimer for polling
func startPolling () {
// setup and start of timer
timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
}
/// method invoked continuously by timer
/// - Note: To keep this method as private I referred this answer at stackoverflow - [Swift - NSTimer does not invoke a private func as selector](http://stackoverflow.com/a/30947182/217586)
#objc private func checkForChangesInPasteboard() {
// check if there is any new item copied
// also check if kind of copied item is string
if let copiedString = pasteboard.stringForType(NSPasteboardTypeString) where pasteboard.changeCount != changeCount {
// obtain url from copied link if its path extension is one of the desired extensions
if let fileUrl = NSURL(string: copiedString) where self.fileKinds.contains(fileUrl.pathExtension!){
// invoke appropriate method on delegate
self.delegate?.newlyCopiedUrlObtained(copiedUrl: fileUrl)
}
// assign new change count to instance variable for later comparison
changeCount = pasteboard.changeCount
}
}
}
Note: in the shared code I am trying to identify if user has copied a
file url or not, the provided code can easily be modified for other general
purposes.
For those who need simplified version of code snippet that gets the job done in Swift 5.7,
it just works (base on #Devarshi code):
func watch(using closure: #escaping (_ copiedString: String) -> Void) {
let pasteboard = NSPasteboard.general
var changeCount = NSPasteboard.general.changeCount
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
guard let copiedString = pasteboard.string(forType: .string),
pasteboard.changeCount != changeCount else { return }
defer {
changeCount = pasteboard.changeCount
}
closure(copiedString)
}
}
how to use is as below:
watch {
print("detected : \($0)")
}
then if you attempt copy any text in your pasteboard, it will watch and print out to the console like below..
detected : your copied message in pasteboard
detected : your copied message in pasteboard
in case, full code sample for how to use it for example in SwiftUI:
import SwiftUI
#main
struct TestApp: App {
var body: some Scene {
WindowGroup {
ContentView()
.onAppear {
watch {
print("detect : \($0)")
}
}
}
}
func watch(using closure: #escaping (_ copiedString: String) -> Void) {
let pasteboard = NSPasteboard.general
var changeCount = NSPasteboard.general.changeCount
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
guard let copiedString = pasteboard.string(forType: .string),
pasteboard.changeCount != changeCount else { return }
defer {
changeCount = pasteboard.changeCount
}
closure(copiedString)
}
}
}
It's not necessary to poll. Pasteboard would generally only be changed by the current view is inactive or does not have focus. Pasteboard has a counter that is incremented when contents change. When window regains focus (windowDidBecomeKey), check if changeCount has changed then process accordingly.
This does not capture every change, but lets your application respond if the Pasteboard is different when it becomes active.
In Swift...
var pasteboardChangeCount = NSPasteboard.general().changeCount
func windowDidBecomeKey(_ notification: Notification)
{ Swift.print("windowDidBecomeKey")
if pasteboardChangeCount != NSPasteboard.general().changeCount
{ viewController.checkPasteboard()
pasteboardChangeCount = NSPasteboard.general().changeCount
}
}
I have a solution for more strict case: detecting when your content in NSPasteboard was replaced by something else.
If you create a class that conforms to NSPasteboardWriting and pass it to -writeObjects: along with the actual content, NSPasteboard will retain this object until its content is replaced. If there are no other strong references to this object, it get deallocated.
Deallocation of this object is the moment when new NSPasteboard got new content.