In one of my Watch Extension's interface controllers I have several WKInterfacePicker elements, and I need to know when the user has selected a value. According to documentation, WKInterfaceController should be able to implement pickerDidSettle(_:) method that has the corresponding picker element as parameter. For some reason the method never gets called when I use the pickers. Here is the basic structure of my implementation:
override func pickerDidSettle(picker: WKInterfacePicker) {
// Code inside this block is not called
}
If I mark the function with an #IBAction attribute and connect them with the picker elements in interface builder, the instance method works. However, this apparently prevents me to assign picker actions that receive all the picker values through which the user is scrolling.
#IBAction
override func pickerDidSettle(picker: WKInterfacePicker) {
// This function gets called, but blocks other actions
}
My interface controller inherits from WKInterfaceController and conforms to two custom protocols. How should I implement the method?
Edit: The issue was related to a possible bug in WatchKit, where pickerDidSettle(_:) will not be called without an existing #IBAction connection to the controller. I assume it is a bug, because related instance methods pickerDidFocus(_:) and pickerDidResignFocus(_:) work independent of the connection.
Sometimes this issue occurs, when something gets 'out of sync' between Xcode and the Simulator.
Just close the Simulator and clean and rebuild your app (via 'Product/Clean Build Folder') to recreate the 'sync.
Related
I have created all my views programatically and to the UIView I have created an extension. This extension is present in a different file called App+Extensions.swift
extension UIView {
func setupParentView() -> UIView {
//...
}
}
The setupParentView() gives me a view with my navbar and background colour. As the design is same everywhere I have used this function. This function is called everywhere in viewDidLoad. So, now in this function the navabar consists of points which need to updated every time the user has purchased/spent it.
So, now as this method is only called in viewDidLoad the function is not called again and the point value do not change in the navigation bar. So, how can I update the point value every time it is changed? I thought of using Combine, but this app will be available for iOS 12 users as well, and I am not using RxSwift, so any help?
Well ViewDidLoad won't get refreshed because your view is now in the stack hierarchy. Some override methods that do get called which have a relation to the view are viewWillAppear, viewDidDissapear, and viewDidAppear.
If your view is going back in forth and the point button needs to be updated everytime your view re-appears consider putting the "refresh" point number in one of the above methods.
Note if your sending info back and forth between two views its also best maybe implement a delegation pattern or an observer.
Use notifications.
In other words, have points be a property of a global object that lives off in "data space" as a singleton. Now just use a property observer so that whenever anyone changes that object's points property, it emits a notification through the NotificationCenter.
That way, any view or view controller that needs to update whenever the points property changes just has to register for that notification when it comes into existence.
[Basically, this is the mechanism, or one of the mechanisms, that you would be replacing or even using directly if you were using Combine or RxSwift.]
Create a custom view called NavBarView
This NavBarView has a property called point
var point = 0 { didSet { updateView() } }
You want to avoid singleton, single view object, so that not everything is coupled together.
You don't need RxSwift or notification to do this.
I'm developing a custom class in Swift based on NSObject. It's a statusMenu icon/menu helper. When I receive an event for the icon being clicked in my custom class, I want to pass this on in the same way an NSButton allows to create an IBAction to respond to the user clicking the button.
How do I do this?
Code:
I'm registering a selector in my class to listen to clicks:
statusItem.action = #selector(statusBarIconClicked)
The selector receiving this:
#objc func statusBarIconClicked(sender: AnyObject) {
print("clicked clicked!!")
// pass sent action on through a new sent action... how?
}
I want this to be linkable to the user in the same way a button can lead to this:
#IBAction func myClassSaysMenuWasClicked(_ sender: Any) {
// Reacting to that
}
Googled for a good while and found: nothing.
I take it that you're asking about this sort of thing, displayed in the Connections inspector (this is iOS, not macOS, but it's the same idea):
The question would then be: when the user selects an instance of my class in the nib editor in Xcode, I'd like those Sent Events to appear in the Connections inspector so that the user can hook up one of them and use the target-action architecture.
You can do this only if your class is a Control subclass. Thus, for example, in iOS, a custom UIControl subclass displays those sent events in Interface Builder.
If you can't do that, then the programmer won't be able to configure your target-action in Interface Builder. You can certainly implement a target–action architecture, but the programmer will have to set the target and action in code. (You could do half a job of it by making the target an outlet, of course.)
I worked around the comment above and googled further. I found the solution being to change from NSObject to NSController in this line:
class StatusMenuController: NSControl, NSMenuDelegate {
And run this command when I want to trigger the sent action:
if let theAction = self.action { NSApp.sendAction(theAction, to: self.target, from: self) }
The if-command of course checking so that an action is actually set before trying to use it.
I found no ways during my research to add any further sent actions. The way to go here seems to be delegates.
I'm building a Safari App Extension using XCode 8.3 and Swift 3, following the Safari App Extension Programming Guide. The extension includes a popover that appears when the extension's toolbar item is clicked. The popover view contains a few buttons linked to actions the user can perform.
I want clicking one of these buttons to close the popover after its action has been performed. By default, clicking anywhere outside of a popover closes it, but I haven't been able to find any other way to close the popover, either in the guide or in the docs.
I know that NSPopover has a performClose method, but there doesn't appear to be a way to access the popover itself from within the extension: the app extension only lets you provide a SFSafariExtensionViewController, whose contents magically appear within the popover.
I've also tried using dismissViewController as described in this StackOverflow answer, but in my view controller self.presenting is always nil, and self.dismissViewController(self) just crashes the extension with the message:
dismissViewController:: Error: maybe this view controller was not presented?.
Lastly, I noticed a related question about programmatically opening the toolbar item popover has gone unanswered the past 6 months. This leads me to suspect Apple may simply have strict limits on how the popover can be opened and closed. Even if this is the case, it would be nice to know for sure what the limitations are.
I'll add an answer in case anyone stumbles upon this question.
A dissmissPopover() instance method has been added to the SFSafariExtensionViewController class. This can be used to programatically close the popover.
The default template given when creating a Safari App Extension in XCode gives you a SafariExtensionViewController class that extends SFSafariExtensionViewController and holds a shared instance as a static field called 'shared', so you can call the dismissPopover() method from that instance.
For example:
class SafariExtensionHandler: SFSafariExtensionHandler {
func myFunc() {
// do stuff;
SafariExtensionViewController.shared.dismissPopover()
// do other stuff;
}
}
I did it by calling dismiss method like below
#IBAction func onLoginBtnClicked (_ sender: Any) {
NSLog("Button clicked")
self.dismiss(self)
}
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I have been trying to learn how delegation with protocols work. I understood everything, but I can't think of when to use delegation other than when using table views and possibly scroll views.
In general, when is delegation used?
What is Delegation?
First of all, you should know that Delegation Pattern is not exclusive for iOS world:
In software engineering, the delegation pattern is a design pattern in
object-oriented programming that allows object composition to achieve
the same code reuse as inheritance.
But working with delegation in the iOS world is so common, I assume that you can see many of classes that provide a delegation/datasource for giving the ability to provide properties or behaviors for the used instance. It is one of main mechanisms of how objects talk to each other in CocoaTouch.
Alternatives:
However, delegation is not the only way to let objects talk to each other in iOS, you might want to know that there are:
NotificationCenter.
KVO (Key-Value Observing).
Completion handlers/Callbacks (using closures).
Target-Action.
Remark: in case if you are interested in comparing between them, you might want to check the following articles:
Communication Patterns.
When to Use Delegation, Notification, or Observation in iOS.
Delegates vs Observers.
When to use Delegation?
So, the question is: "So why should I use delegation instead of those options?"
I will try to make it simple; I would suggest the use of delegation when you have one to one relationship between two objects. Just to make it clearer, the goal of talking a little bit about the NotificationCenter is to try to make sense when delegations are used:
NotificationCenter represents one to many relationship; Simply, it works as: posting (notifying) a notification on a specific event and observing (get notified about) this notification -- it could be observed anywhere else; Logically, that's what one to many relationship means. It is a representation of the Observer Pattern.
How to Apply Delegation?
For the purpose of simplifying, I would mention it as steps:
Knowing the requirements: Each delegate has its own rules, listed in the delegate protocol which is a set of method signatures that you should implement for conforming this delegation.
Conforming for the delegation: it is simply letting your class to be a delegate, by marking it. For instance: class ViewController: UIViewController, UITableViewDelegate {}.
Connecting the delegate object: Marking your class to be a delegate is not enough, you need to make sure that the object you want to be confirmed by your class to give the required job to your class.
Implementing the requirements: Finally, your class have to implement all required methods listed in the delegate protocol.
For Example
Does it sounds a little confusing? What about a real-world example?
Consider the following scenario:
Imagine that you are building an application related to playing audios. Some of the viewControllers should have a view of an audio player. In the simplest case, we assume that it should have a play/pause button and another button for, let's say, showing a playlist somehow, regardless of how it may look like.
So far so good, the audio player view has its separated UIView class and .xib file; it should be added as a subview in any desired viewController.
Now, how can you add functionality to both of the buttons for each viewController? You might think: "Simply, I will add an IBAction in the view class and that's it", at first look, it might sound ok, but after re-thinking a little bit, you will realize that it will not be applicable if you are trying to handle the event of tapping the button at the controller layer; To make it clear, what if each viewController implemented different functionality when tapping the buttons in the audio player view? For example: tapping the playlist in "A" viewController will display a tableView, but tapping it in the "B" viewController will display a picker.
Well, let's apply Delegation to this issue:
The "#" comments represents the steps of "How to Apply Delegation?" section.
Audio Player View:
// # 1: here is the protocol for creating the delegation
protocol AudioPlayerDelegate: class {
func playPauseDidTap()
func playlistDidTap()
}
class AudioPlayerView: UIView {
//MARK:- IBOutlets
#IBOutlet weak private var btnPlayPause: UIButton!
#IBOutlet weak private var btnPlaylist: UIButton!
// MARK:- Delegate
weak var delegate: AudioPlayerDelegate?
// IBActions
#IBAction private func playPauseTapped(_ sender: AnyObject) {
delegate?.playPauseDidTap()
}
#IBAction private func playlistTapped(_ sender: AnyObject) {
delegate?.playlistDidTap()
}
}
View Controller:
class ViewController: UIViewController {
var audioPlayer: AudioPlayerView?
// MARK:- Life Cycle
override func viewDidLoad() {
super.viewDidLoad()
audioPlayer = AudioPlayerView()
// # 3: the "AudioPlayerView" instance delegate will implemented by my class "ViewController"
audioPlayer?.delegate = self
}
}
// # 2: "ViewController" will implement "AudioPlayerDelegate":
extension ViewController: AudioPlayerDelegate {
// # 4: "ViewController" implements "AudioPlayerDelegate" requirments:
func playPauseDidTap() {
print("play/pause tapped!!")
}
func playlistDidTap() {
// note that is should do a different behavior in each viewController...
print("list tapped!!")
}
}
Quick Tip:
As one of the most popular examples of using delegation is Passing Data Back between View Controllers.
Delegation is used when you want to pass some information or state of object A to another object B. Usually object B is the object that created object A.
I will list some situations where you would use delegation.
Yes you're right. table views and scroll views use delegates because they want to tell whoever is interested (usuall your view controller) that "someone selected a row!" or "someone scrolled the scroll view!". Not only do scroll views and table views use delegates, UITextField and UIDatePicker and a lot of other views use delegates too!
View Controllers also have delegates. For example, UIImagePickerController. The reason why is roughly the same as above - because the UIImagePickerController wants to tell you messages like "an image has been selected!". Another example would be UIPopoverControllerDelegate. This delegate tells you things like "the popover has been dismissed!"
Other classes that use delegates include CLLocationManager. This delegate tells you things like "the user's location has been detected" or "failed to detect the user's location".
You can use delegation in your code when a certain view controller of yours wants to send messages to other view controllers. If it is a settings view controller, it might send messages like "the font size setting has been changed!" and the view controller that cares about the font size setting changing will know and change the font size of a label or something.
Delegate Method to Selectionimages
Create baseClass And Insert the following code
Create Another class then insert code
Delegation in IOS world and mostly in MVC (Model View Controller)
is a way for the View to talk to the Controller and it's called "blind communication"
and delegation means to give the " leading stick " to another object ( doesn't really care who is taking over but usually the Controller) to control over components that the view can not control on it's own (remember it's only a view) or doesn't own
to make it more simple ....
the controller can talk to a view but the view can not talk to the controller without Delegation
Is there a way to detect when the pullToRefresh has been called on a Parse - PFQueryTableViewController?
I've found some of that on objective-c, but nothing on swift.
As far as I know, pullToRefresh is a private implementation, so you can't override it to detect calls. However, pulling to refresh will trigger the loadObjects function, which in turn triggers the objectsWillLoad and objectsDidLoad methods. You can override the 2 methods to do whatever you want to do.
The only drawback is that objectsWillLoad and the did load counterpart will be called even when the view is initially displayed.