While entering into state I want to pass parameters with state as follows:
playerStateMachine.enter(pauseState.self, ["score":123, "rank":1])
so I can get that value as follows in didEnter method:
class pauseState: GKState {
var userinfo:[String:Any]?
init(player: SSGameDelegate) {
super.init(player: player)
}
override func didEnter(from previousState: GKState?) {
super.didEnter(from: previousState)
//Access input value here
print(userinfo["score"])
print(userinfo["rank"])
}
}
You don’t pass parameter this way. In you current state,there is a function.
func willExit(to nextState: GKState)
You can pass parameters over there as nextState.userinfo[score] = 111
If you keep track of the state Machine states, you are able to set a parameter before entering the state. I am not totally sure this is thread safe, I will update as I test further will usage.
let alienWaitState = AlienWaitState(game: self)
let alienFlyingState = AlienFlyingState(game: self)
aliensStateMachine = GKStateMachine(states: [
alienWaitState,
alienFlyingState,
AlienAnimateOffState(game: self),
AlienDeadRemovalState(game: self)
])
in this case alienState parameter "associatedAlienName" can be set before entry to the state
alienWaitState.associatedAlienName = newAlien.name
aliensStateMachine.enter(AlienWaitState.self)
AlienState class, alienWaitState is a subclass
class AlienState: GKState {
weak var game:GameScene?
var associatedAlienName:String?
....
Related
I have a view controller that shows detail for my "SkillGroup" entity. I want to use this for both viewing and editing/creating a "SkillGroup". Thus I have an optional variable skillGroup which is either unset - and nil when you are first creating the SkillGroup and before you save it, OR it is set and you will be simply viewing the SkillGroup. Here is my code
class GroupViewController:UIViewController {
var skillGroup: SkillGroup?
override func viewDidLoad() {
super.viewDidLoad()
if let skillGroup = skillGroup {
self.title = skillGroup.name
}
}
}
and in the previous view controller:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "createGroupSegue" {
let destination = segue.destination as? GroupViewController
destination?.createOrEdit = true
}
if segue.identifier == "showGroupSegue" {
if let selectedGroupPath = self.groupsTableView.indexPathForSelectedRow {
let destination = segue.destination as? GroupViewController
destination?.createOrEdit = false
let group = groups[selectedGroupPath.row]
destination?.skillGroup = group
}
}
}
If I set a breakpoint right after the call to super, and I inspect skillGroup, it says its <uninitialized>. I don't think this because its "nil" like a normal optional variable that hasn't been set. Additionally I did set the skillGroup variable in the prepare for segue code.
I really can't find much information on what means. Can someone help me out here?
I think you are inspecting the wrong variable in the debugger (the local variable instead of the instance variable).
I made a quick sample:
class ViewController: UIViewController {
public class TestClass {
var foo: String
var bar: Int
init() {
foo = "foo"
bar = 4711
}
}
public var test: TestClass?
override func viewDidLoad() {
super.viewDidLoad()
test = TestClass()
if let test = test {
print(test.foo)
}
}
}
When I set a breakpoint on the line if let test = test { I will see the following in the debugger:
Here you can see that it will print <uninitialized> when I print the description of the local test variable because the let statement on that line was not executed yet.
Please note that there is a local variable (only living inside the if scope) and an instance variable. In the debugger you will see the instance variables when you expand the self node.
I was going through Apple documentation and some tutorials where I learnt we can set observer which will be called if object if modified. But I have few doubts in my mind.
Here is a summary where a model is notified about the property changes:
Suppose there are 3 view controllers and they show listing of Foo models. Foo model has properties called id and title. My question is, is it feasible to get notified in others controllers that Foo model is modified which is having id 10 for example. Is that possible only if same instance of model is shared between 3 controllers, or we can achieve it although instances are different?
I am looking for a concrete solution, where a user like a feed (similar as Facebook) in one screen and if a feed with same id is in other controller, that controller should be notified that this feed is modified, refresh its UI. I have attached an image for clear idea.
I do not wish to go with delegate or notification pattern as it might create chaos, rather observer pattern will be more proper solution.
Here is an example of how you can achieve this.
Feed Model:
class Feed: NSObject {
var id: String
#objc dynamic var isLiked = false
init(id: String) {
self.id = id
}
}
Any property that you want to observe, mark it #objc dynamic, i.e. isLiked in Feed model.
class ListVC: UIViewController {
let feed = Feed(id: "1")
var observer: NSKeyValueObservation?
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func openDetailVC(_ sender: UIButton) {
if let detailVC = self.storyboard?.instantiateViewController(withIdentifier: "DetailVC") as? DetailVC {
self.observer = detailVC.feed.observe(\.isLiked, options: [.new], changeHandler: { (feed, change) in
if let newValue = change.newValue {
print(newValue)
//Reload the UI here...
}
})
self.navigationController?.pushViewController(detailVC, animated: true)
}
}
}
Next there is a ListVC that has a feed property.
Add an observer to feed in viewDidLoad(). Specify the property that you want to observe in feed i.e. isLiked. The closure in the observer will be called every time there is a change in isLiked property.
Now, DetailVC will be.
class DetailVC: UIViewController {
let feed = Feed(id: "1")
#IBAction func likeButtonPressed(_ sender: UIButton) {
self.feed.isLiked = !self.feed.isLiked
}
}
In the above code, I'm changing the value of isLiked property in feed whenever likeButton is pressed.
I'm trying to send a Signal from one ViewModel to another one. Basically I want the second ViewModel to use the same Signal as the first ViewModel, but I also need the initial value at init state in the second ViewModel . So far I have manage to solve this by sending the Signal<Person, NoError> and the Person model.
struct Person {
let name: String
let age: Int
}
In PersonListViewModel the Signal is defined as output where the stream is handled.
protocol PersonListViewModelOutputs {
var goToPersonDetail: Signal<Person, NoError> { get }
}
PersonDetailViewModel:
protocol PersonDetailViewModelInputs {
func viewDidLoad()
func configureWith(personSignal: Signal<Person, NoError>, initialPerson: Person)
}
protocol PersonDetailViewModelOutputs {
var person: Signal<Person, NoError> { get }
}
protocol PersonDetailViewModelType {
var inputs: PersonDetailViewModelInputs { get }
var outputs: PersonDetailViewModelOutputs { get }
}
public final class PersonDetailViewModel: PersonDetailViewModelType, PersonDetailViewModelInputs, PersonDetailViewModelOutputs {
init(){
self.person = self.configureWithPersonPropery.signal.skipNil()
}
private let configureWithPersonProperty = MutableProperty<Person?>(nil)
func configureWith(personSignal: Signal<Person, NoError>, initialPerson: Person) {
configureWithPersonProperty.value = initialPerson
configureWithPersonProperty <~ personSignal.producer
}
}
However this solution seems to bring unnecessary parameter inside func configureWith(...) and I guess there could be a better way to solve it.
For example, is it possible to get the last emitted value from personSignal: Signal<Person, NoError> inside func configureWith(...) without sending the Person Struct?
Since your signal is NoError, you can just pass in a Property instance instead of a Signal. A property is basically a signal that is guaranteed to have a value and can't send an error. You can create one with an initial value and an existing signal:
let prop = Property(initial: initialPerson, then: signal)
I have a variable globalVariable declared at global scope that may change at any time.
Different ViewControllers in my app need to react differently, when globalVariable changes.
Thus it would be desirable to add a property observer in each ViewController that execute the needed code when globalVariable changes.
I cannot seem to achieve it with override or extension. What is the way to go here?
If your goal is to simply know when your global variable changed, you could have it post a notification upon change:
extension NSNotification.Name {
static let globalVariableChanged = NSNotification.Name(Bundle.main.bundleIdentifier! + ".globalVariable")
}
var globalVariable: Int = 0 {
didSet {
NotificationCenter.default.post(name: .globalVariableChanged, object: nil)
}
}
Then any object can add an observer for that notification:
class ViewController: UIViewController {
private var observer: NSObjectProtocol!
override func viewDidLoad() {
super.viewDidLoad()
// add observer; make sure any `self` references are `weak` or `unowned`; obviously, if you don't reference `self`, that's not necessary
observer = NotificationCenter.default.addObserver(forName: .globalVariableChanged, object: nil, queue: .main) { [weak self] notification in
// do something with globalVariable here
}
}
deinit {
// remember to remove it when this object is deallocated
NotificationCenter.default.removeObserver(observer)
}
}
Note, this didSet mechanism will not detect changes if (a) the global variable is a reference type, i.e. a class; and (b) it merely mutates the object that the global variable references rather than replacing it with a new instance. To identify that scenario, you need to use KVO or other mechanism to detect mutation.
There can be only one didSet{} function for your global variable and it must belong to the variable itself. What you can do is make the variable's didSet{} function call a list of functions from other objects.
You could use notifications for this or you could build your own mechanism.
Here's an example of how you could create your own mechanism:
(note that this is pretty generic and could work for any variable types or singleton instance)
// Container for an observer's function reference
// - will be used to call the observer's code when the variable is set
// - Separates the object reference from the function reference
// to avoid strong retention cycles.
struct GlobalDidSet<T>
{
weak var observer:AnyObject?
var didSetFunction:(AnyObject)->(T)->()
init(_ observer:AnyObject, didSet function:#escaping (AnyObject)->(T)->())
{
self.observer = observer
didSetFunction = function
}
}
// Container for a list of observers to be notified
// - maintains the list of observers
// - automatically clears entries that non longer have a valid object
// - calls all observers when variable changes
// - erases type of observer to allow generic use of GlobalDidSet<>
struct GlobalDidSets<T>
{
var observers : [GlobalDidSet<T>] = []
mutating func register<O:AnyObject>(_ observer:O, didSet function:#escaping (O)->(T)->())
{
let observer = GlobalDidSet<T>(observer)
{ (object:AnyObject) in function(object as! O) }
observers.append(observer)
}
mutating func notifyDidSet(_ oldValue:T)
{
observers = observers.filter{$0.observer != nil}
observers.forEach{ $0.didSetFunction($0.observer!)(oldValue) }
}
}
...
// To use this, you will need a second variable to manage the list of observers
// and your global variable's didSet{} must use that observer list
// to perform the multiple function calls
//
var globalVariableDidSets = GlobalDidSets<String>()
var globalVariable : String = "Initial Value"
{
didSet { globalVariableDidSets.notifyDidSet(oldValue) }
}
// In your view controllers (or any other class), you need to setup the
// reaction to the global variable changes by registering to the observer list
//
class MyVC:UIViewController
{
override func viewDidLoad()
{
globalVariableDidSets.register(self){ $0.handleVariableChange }
// ...
}
func handleVariableChange(_ oldValue:String)
{
//...
}
}
I need to execute a function when a variable value changes.
I have a singleton class containing a shared variable called labelChange. Values of this variable are taken from another class called Model. I have two VC classes, one of them has a button and a label and the second only a button.
When the button in the first VC class is pressed I am updating the label with this func:
func updateLabel(){
self.label.text = SharingManager.sharedInstance.labelChange
}
But I want to call the same method whenever the value of the labelChange is changed. So in button click I will only update the labelChange value and when this thing happen I want to update the label with the new value of the labelChange. Also in the second VC I am able to update the labelChange value but I am not able to update the label when this value is changed.
Maybe properties are the solution but can anyone show me how to do so.
Edited second time:
Singleton Class:
class SharingManager {
func updateLabel() {
println(labelChange)
ViewController().label.text = SharingManager.sharedInstance.labelChange
}
var labelChange: String = Model().callElements() {
willSet {
updateLabel()
}
}
static let sharedInstance = SharingManager()
}
First VC:
class ViewController: UIViewController {
#IBOutlet weak var label: UILabel!
#IBAction func Button(sender: UIButton) {
SViewController().updateMessageAndDismiss()
}
}
Second VC:
func updateMessageAndDismiss() {
SharingManager.sharedInstance.labelChange = modelFromS.callElements()
self.dismissViewControllerAnimated(true, completion: nil)
}
#IBAction func b2(sender: UIButton) {
updateMessageAndDismiss()
}
I made some improvements but I need to reference a label from the first VC class in singleton. Therefore I will update that label of VC in singleton.
When I print the value of labelChange the value is being updated and everything is fine. But when I try to update that value on label from singleton I receive an error:
unexpectedly found nil while unwrapping an Optional value
and the error is pointing in 4th line of singleton class.
You can simply use a property observer for the variable, labelChange, and call the function that you want to call inside didSet (or willSet if you want to call it before it has been set):
class SharingManager {
var labelChange: String = Model().callElements() {
didSet {
updateLabel()
}
}
static let sharedInstance = SharingManager()
}
This is explained in Property Observers.
I'm not sure why this didn't work when you tried it, but if you are having trouble because the function you are trying to call (updateLabel) is in a different class, you could add a variable in the SharingManager class to store the function to call when didSet has been called, which you would set to updateLabel in this case.
Edited:
So if you want to edit a label from the ViewController, you would want to have that updateLabel() function in the ViewController class to update the label, but store that function in the singleton class so it can know which function to call:
class SharingManager {
static let sharedInstance = SharingManager()
var updateLabel: (() -> Void)?
var labelChange: String = Model().callElements() {
didSet {
updateLabel?()
}
}
}
and then set it in whichever class that you have the function that you want to be called, like (assuming updateLabel is the function that you want to call):
SharingManager.sharedInstance.updateLabel = updateLabel
Of course, you will want to make sure that the view controller that is responsible for that function still exists, so the singleton class can call the function.
If you need to call different functions depending on which view controller is visible, you might want to consider Key-Value Observing to get notifications whenever the value for certain variables change.
Also, you never want to initialize a view controller like that and then immediately set the IBOutlets of the view controller, since IBOutlets don't get initialized until the its view actually get loaded. You need to use an existing view controller object in some way.
Hope this helps.
In Swift 4 you can use Key-Value Observation.
label.observe(\.text, changeHandler: { (label, change) in
// text has changed
})
This is basically it, but there is a little catch. "observe" returns an NSKeyValueObservation object that you need to hold! - when it is deallocated, you’ll receive no more notifications. To avoid that we can assign it to a property which will be retained.
var observer:NSKeyValueObservation?
// then assign the return value of "observe" to it
observer = label.observe(\.text, changeHandler: { (label, change) in
// text has changed,
})
You can also observe if the the value has changed or has been set for the first time
observer = label.observe(\.text, changeHandler: { (label, change) in
// just check for the old value in "change" is not Nil
if let oldValue = change.oldValue {
print("\(label.text) has changed from \(oldValue) to \(label.text)")
} else {
print("\(label.text) is now set")
}
})
For More Information please consult Apples documentation here
Apple provide these property declaration type :-
1. Computed Properties:-
In addition to stored properties, classes, structures, and enumerations can define computed properties, which do not actually store a value. Instead, they provide a getter and an optional setter to retrieve and set other properties and values indirectly.
var otherBool:Bool = false
public var enable:Bool {
get{
print("i can do editional work when setter set value ")
return self.enable
}
set(newValue){
print("i can do editional work when setter set value ")
self.otherBool = newValue
}
}
2. Read-Only Computed Properties:-
A computed property with a getter but no setter is known as a read-only computed property. A read-only computed property always returns a value, and can be accessed through dot syntax, but cannot be set to a different value.
var volume: Double {
return volume
}
3. Property Observers:-
You have the option to define either or both of these observers on a property:
willSet is called just before the value is stored.
didSet is called immediately after the new value is stored.
public var totalSteps: Int = 0 {
willSet(newTotalSteps) {
print("About to set totalSteps to \(newTotalSteps)")
}
didSet {
if totalSteps > oldValue {
print("Added \(totalSteps - oldValue) steps")
}
}
}
NOTE:- For More Information go on professional link
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html
There is another way of doing so, by using RxSwift:
Add RxSwift and RxCocoa pods into your project
Modify your SharingManager:
import RxSwift
class SharingManager {
static let sharedInstance = SharingManager()
private let _labelUpdate = PublishSubject<String>()
let onUpdateLabel: Observable<String>? // any object can subscribe to text change using this observable
// call this method whenever you need to change text
func triggerLabelUpdate(newValue: String) {
_labelUpdate.onNext(newValue)
}
init() {
onUpdateLabel = _labelUpdate.shareReplay(1)
}
}
In your ViewController you can subscribe to value update in two ways:
a. subscribe to updates, and change label text manually
// add this ivar somewhere in ViewController
let disposeBag = DisposeBag()
// put this somewhere in viewDidLoad
SharingManager.sharedInstance.onUpdateLabel?
.observeOn(MainScheduler.instance) // make sure we're on main thread
.subscribeNext { [weak self] newValue in
// do whatever you need with this string here, like:
// self?.myLabel.text = newValue
}
.addDisposableTo(disposeBag) // for resource management
b. bind updates directly to UILabel
// add this ivar somewhere in ViewController
let disposeBag = DisposeBag()
// put this somewhere in viewDidLoad
SharingManager.sharedInstance.onUpdateLabel?
.distinctUntilChanged() // only if value has been changed since previous value
.observeOn(MainScheduler.instance) // do in main thread
.bindTo(myLabel.rx_text) // will setText: for that label when value changed
.addDisposableTo(disposeBag) // for resource management
And don't forget to import RxCocoa in ViewController.
For triggering event just call
SharingManager.sharedInstance.triggerLabelUpdate("whatever string here")
HERE you can find example project. Just do pod update and run workspace file.
var item = "initial value" {
didSet { //called when item changes
print("changed")
}
willSet {
print("about to change")
}
}
item = "p"
override var isHighlighted: Bool {
get { super.isHighlighted }
set {
super.isHighlighted = newValue
if newValue {
label.textColor = highlightedTextColor
contentView.backgroundColor = highlightedBackgroundColor
} else {
label.textColor = normalTextColor
contentView.backgroundColor = normalBackgroundColor
}
}
}