In my app I have a function where I want it to print something depending on the current view controller that is loaded. I do this by setting a global variable (Bool) and then toggling the flags in the view controller classes. From my main class I have something like this:
var FirstViewControllerisVisible: Bool = false
var SecondViewControllerisVisible: Bool = false
var ThirdViewControllerisVisible: Bool = false
#objc func PlayAgainfunc(_ sender: Any) {
if counter % 15 == 0 {
if FirstViewControllerisVisible == true {
print("First View Controller is visible")
} else if SecondViewControllerisVisible == true {
print("Second View Controller is visible")
} else if ThirdViewControllerisVisible == true {
print("Third View Controller is visible")
}
}
counter += 1
}
Then, in those classes I can set the flags like this:
override func viewDidAppear(_ animated: Bool) {
FirstViewControllerisVisible = true
}
override func viewDidDisappear(_ animated: Bool) {
FirstViewControllerisVisible = false
}
This worked great when it was exclusively Swift, but the problem with global variables is that they can't be accessed by Objective-C. I can't find a way to set flags in my ObjC classes and then check if true or false. For instance, If I tried:
- (void)viewDidAppear:(BOOL)animated; {
[(FirstViewControllerisVisible) == true];
}
- (void)viewDidDisappear:(BOOL)animated; {
[(FirstViewControllerisVisible) == false];
}
I would get the error 'use of undeclared identifier' because my global vars declared in Swift are Swift only.
After the view controller has loaded, you can
if let viewController = UIApplication.shared.keyWindow?.rootViewController {
print(type(of: viewController))
}
add below mentioned extension. you will get the desired result.
extension UIApplication {
/// will return currently showing view controller
static var topMostViewController: UIViewController? {
return UIApplication.shared.keyWindow?.rootViewController?.visibleViewController
}
}
extension UIViewController {
/// The visible view controller from a given view controller
var visibleViewController: UIViewController? {
if let navigationController = self as? UINavigationController {
return navigationController.topViewController?.visibleViewController
} else if let tabBarController = self as? UITabBarController {
return tabBarController.selectedViewController?.visibleViewController
} else if let presentedViewController = presentedViewController {
return presentedViewController.visibleViewController
} else {
return self
}
}
}
and access it like:
let viewController = UIApplication.topMostViewController
Happy Coding
Related
Navigation rootViewController is dependent on user set up due to that I have tried to check if user did do all the onboarding forms before the main screen launch. My question is how to set inatial value to UserDefaults in my navigation. This always prints "false"
extension UserDefaults {
var didUserSetUp: Bool? {
get {
///// Register the app default:
/// Initialize value from UserDefaults returns false
UserDefaults.standard.register(defaults: ["didUserSetUp" : false])
return UserDefaults.standard.bool(forKey: "didUserSetUp")
}
set {
/// Set value to UserDefaults
UserDefaults.standard.set(newValue, forKey: "didUserSetUp")
}
}
}
The way is set it in code:
UserDefaults.standard.didUserSetUp = false
if UserDefaults.standard.didUserSetUp { }
You'd need to show example code of how you're attempting to use the property you've created, but I tried what you've shown here, and was able to get it working as expected. Here's what I did:
extension UserDefaults {
var didCompleteOnboarding: Bool? {
get {
UserDefaults.standard.register(defaults: ["didCompleteOnboarding": false])
return UserDefaults.standard.bool(forKey: "didCompleteOnboarding")
}
set {
UserDefaults.standard.set(newValue, forKey: "didCompleteOnboarding")
}
}
}
Then in the root view controller:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
UserDefaults.standard.didCompleteOnboarding = true
print(UserDefaults.standard.didCompleteOnboarding ?? false)
}
}
Prints true in the console.
I have gameCenterButton in VC1. Its purpose is to take the user to Game Center's Leaderboards where they can see High Scores. If the user decides to authenticate with Game Center, then I want to change gameCenterButton's state (un-grey and enable). In my GameKitHelper class I have these:
func authenticateLocalPlayer() {
GKLocalPlayer.local.authenticateHandler =
{ (viewController, error) in
self.gameCenterEnabled = false
if viewController != nil {
self.authenticationViewController = viewController
NotificationCenter.default.post(name: NSNotification.Name(
GameKitHelper.PresentAuthenticationViewController),
object: self)
} else if GKLocalPlayer.local.isAuthenticated {
self.gameCenterEnabled = true
}
}
}
extension GameKitHelper: GKGameCenterControllerDelegate {
func gameCenterViewControllerDidFinish(_ gameCenterViewController: GKGameCenterViewController) {
gameCenterViewController.dismiss(animated: true, completion: nil)
}
}
In VC1 I have this:
#IBOutlet weak var gameCenterButton: UIButton!
#IBAction func gameCenter(_ sender: UIButton) {
GameKitHelper.sharedInstance.showGKGameCenterViewController(viewController: self)
}
I'm thinking that inside of extension GameKitHelper I can do ...
if gameCenterEnabled == true {
gameCenterButton.isEnabled = true // How do I allow for this?
gameCenterButton.alpha = 1 // How do I allow for this?
How do I allow gameCenterButton state to change outside of it's class. Is there something I need to do in AppDelegate?
Put var gameCenterEnabled = false outside (above) of your GameKitHelper class, thus making it "global". You will likely be prompted to remove the self. in self.gameCenterEnabled = false and in self.gameCenterEnabled = true. Do so.
Now, you can reference gameCenterEnabled in VC1's class and change gameCenterButton's state like this:
// code to determine gameCenterButton's state based on gameCenterEnabled's status
if gameCenterEnabled == false {
self.gameCenterButton.isEnabled = false
self.gameCenterButton.alpha = 0.37
} else {
self.gameCenterButton.isEnabled = true
self.gameCenterButton.alpha = 1
}
Consider the following simplified code example. It's presented here in Swift, but the same behavior occurs in objective-c.
import Foundation
import Cocoa
class MainWindow : NSWindow {
#IBAction func onClick_openFile(sender : AnyObject?) {
let path = runOpenPanel(false);
NSLog(path as String)
}
#IBAction func onClick_crashyByeBye(sender : AnyObject?) {
let path = runOpenPanel(true);
NSLog(path as String)
}
private func runOpenPanel(useCrashyDelegate : Bool) -> NSString {
let openPanel = NSOpenPanel.init()
openPanel.canChooseDirectories = false
openPanel.canChooseFiles = true
openPanel.allowsMultipleSelection = false
let safeDelegate = MyOpenPanelDelegate.init() //same scope as openPanel.runModal()--works fine
if (useCrashyDelegate) {
let crashyDelegate = MyOpenPanelDelegate.init() //falls out of scope before openPanel.runModal() and crashes
openPanel.delegate = crashyDelegate
} else {
openPanel.delegate = safeDelegate
}
if (openPanel.runModal() == NSFileHandlingPanelOKButton && openPanel.URLs.count == 1) {
return openPanel.URLs[0].path!
}
return ""
}
}
class MyOpenPanelDelegate : NSObject, NSOpenSavePanelDelegate {
func panel(sender: AnyObject, shouldEnableURL url: NSURL) -> Bool {
var isDir : ObjCBool = false
if (NSFileManager.defaultManager().fileExistsAtPath(url.path!, isDirectory: &isDir)) {
return isDir || (url.path! as NSString).lastPathComponent.lowercaseString == "foo.txt"
}
return false
}
}
When the useCrashyDelegate argument to runOpenPanel is true, crashyDelegate is instantiated in a nested scope and falls out of scope before the call to openPanel.runModal(). Since the open panel assigns crashyDelegate as its delegate, I would expect crashyDelegate's reference count to be incremented. However, the application crashes with an EXC_BAD_ACCESS when useCrashyDelegate is true. If useCrashyDelegate is false, safeDelegate, which is instantiated in the same scope as the call to openPanel.runModal(), is assigned to the open panel and there is no EXC_BAD_ACCESS.
This is leading me to believe that NSOpenPanel is not incrementing its delegate's reference count. Is this the expected behavior, or might this be a bug?
This is leading me to believe that NSOpenPanel is not incrementing its delegate's reference count. Is this the expected behavior, or might this be a bug?
It is expected. Check the type of the property and you will see it is assign (Objective-C) or unsafe (Swift), a strong reference is not kept. This is a common design pattern for Cocoa delegates.
HTH
I am upgrading my code from iOS 8 to iOS 9. I have a code snippet in my program
[[UIApplication applicationName] setStatusBarHidden:YES];.
I am getting the warning "setStatusBarHidden is deprecated in iOS 9.0, Use -[UIViewController prefersStatusBarHidden". If I just replace 'setStatusBarHidden' with 'prefersStatusBarHidden', I get 'instance method not found'.
Can someone please suggest me how to solve this problem?
Add below code to your view controller..
- (BOOL)prefersStatusBarHidden {
return NO;
}
Note :
If you change the return value for this method, call the
setNeedsStatusBarAppearanceUpdate method.
For childViewController, To specify that a child view controller
should control preferred status bar hidden/unhidden state, implement
the childViewControllerForStatusBarHidden method.
prefersStatusBarHidden is available from iOS 7+.
Use this in Your UIViewController class
var isHidden = true{
didSet{
self.setNeedsStatusBarAppearanceUpdate()
}
}
override var prefersStatusBarHidden: Bool {
return isHidden
}
If you change the return value for this method, call the
setNeedsStatusBarAppearanceUpdate() method. To specify that a child
view controller should control preferred status bar hidden/unhidden
state, implement the childViewControllerForStatusBarHidden method.
you have to add method in yourViewController.m
- (BOOL)prefersStatusBarHidden {
return NO;
}
Swift 3.1 Xcode 8.2.1
Change in info.plist the row View controller-based status bar appearance and set it to NO
In your target settings tick "Hide Status bar"
Both steps are required
Here is my swift code for setting status bar hidden and style.
extension UIViewController {
public var privateStatusBarHidden: Bool {
return statusBarHidden
}
public var privateStatusBarStyle: UIStatusBarStyle {
return statusBarStyle
}
public func setStatusBarHidden(hidden: Bool, animated: Bool = false) {
statusBarHidden = hidden
if animated {
UIView.animate(withDuration: 0.25, animations: {
self.setNeedsStatusBarAppearanceUpdate()
})
} else {
self.setNeedsStatusBarAppearanceUpdate()
}
}
public func setStatusBar(style: UIStatusBarStyle) {
statusBarStyle = style
self.setNeedsStatusBarAppearanceUpdate()
}
public static func swizzleStatusBarHiddenPropertyForViewController() {
var original = class_getInstanceMethod(UIViewController.self, #selector(getter: UIViewController.prefersStatusBarHidden))
var changeling = class_getInstanceMethod(UIViewController.self, #selector(getter: UIViewController.privateStatusBarHidden))
method_exchangeImplementations(original, changeling)
original = class_getInstanceMethod(UIViewController.self, #selector(getter: UIViewController.preferredStatusBarStyle))
changeling = class_getInstanceMethod(UIViewController.self, #selector(getter: UIViewController.privateStatusBarStyle))
method_exchangeImplementations(original, changeling)
original = class_getClassMethod(UIViewController.self, #selector(UIViewController.swizzleStatusBarHiddenPropertyForViewController))
changeling = class_getClassMethod(UIViewController.self, #selector(UIViewController.emptyFunction))
method_exchangeImplementations(original, changeling)
}
#objc private static func emptyFunction() {}
}
Usage
in lauching function
UIViewController.swizzleStatusBarHiddenPropertyForViewController()
for hide/show statusBar, in UIViewController
. self.setStatusBar(hidden: true/false)
Swift 3 with Xcode 8.3.3
1) Add a row in you Info.plist.
2) In your ViewController ViewDidLoad() override add:
UIApplication.shared.isStatusBarHidden = true
In Objective-C you would do something along the lines of
- (BOOL)isEqual:(id)other {
if (other == self)
return YES;
if (!other || ![other isKindOfClass:[self class]])
return NO;
return [self.customProperty isEqual:other.customProperty];
}
My first naive attempt in swift goes as follows
func isEqual(other: AnyObject) -> Boolean {
if self === other {
return true
}
if let otherTyped = other as? MyType {
return self.myProperty == otherTyper.myProperty
}
return false
}
But I'm far from being happy with it. I don't even know whether the signature is right or whether we're supposed to use anything different than isEqual.
Any thoughts?
EDIT:
I'd also like to keep Objective-C compatibility (my class is used in both legacy Obj-C code and new Swift code). So I think only overriding == isn't enough. Am I wrong?
Yes, you need to override isEqual (and hash) to make your objects fully Objective-C compatible. Here's a Playground-ready example for the syntax:
import Foundation
class MyClass: NSObject {
var value = 5
override func isEqual(object: AnyObject?) -> Bool {
if let object = object as? MyClass {
return value == object.value
} else {
return false
}
}
override var hash: Int {
return value.hashValue
}
}
var x = MyClass()
var y = MyClass()
var set = NSMutableSet()
x.value = 10
y.value = 10
set.addObject(x)
x.isEqual(y) // true
set.containsObject(y) // true
(syntax current as of Xcode 6.3)
You could also implement a custom equatable, for instance:
func == (lhs: CustomClass, rhs: CustomClass) -> Bool {
return lhs.variable == rhs.variable
}
This will allow you to simply check equality like this:
let c1: CustomClass = CustomClass(5)
let c2: CustomClass = CustomClass(5)
if c1 == c2 {
// do whatever
}
Be sure your custom equatable is outside the class scope!
swift3 sig:
open override func isEqual(_ object: Any?) -> Bool {
guard let site = object as? PZSite else {
return false
}
....
}
In Swift you can override infix operators (and even make your own). See here.
So rather than using isEqual you could do:
myType == anotherType
One more example
public class PRSize: NSObject {
public var width: Int
public var height: Int
public init(width: Int, height: Int) {
self.width = width
self.height = height
}
static func == (lhs: PRSize, rhs: PRSize) -> Bool {
return lhs.width == rhs.width && lhs.height == rhs.height
}
override public func isEqual(_ object: Any?) -> Bool {
if let other = object as? PRSize {
if self === other {
return true
} else {
return self.width == other.width && self.height == other.height
}
}
return false
}
override public var hash : Int {
return "\(width)x\(height)".hashValue
}
}
To archive Objective-C compatibility you have to override isEqual method as described on page 16 of this document: https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/BuildingCocoaApps.pdf