Working on my first SwiftUI Project.
Trivial in UIKit since all Views are Classes.
Now, when I try to create a function that returns Views contrained to a type:
protocol RootView : View {
func left() -> View // 1
func right() -> View // 2
}
func viewFor(_ i : Int) -> RootView { //3
}
1,2 & 3 throw "Protocol View can only be used as a generic constrain....."
I have tried a bazillion combinations (using associated type in RootView, #ViewBuilder, etc)
just keeping it simple,
How can we return a protocol-bound View from a function in SwiftUI?
sorry if the solution is elemental, started SwiftUI precisely a week ago
You need to use generics, like
protocol RootView : View {
associatedtype LeftView: View
associatedtype RightView: View
func left() -> LeftView // 1
func right() -> RightView // 2
}
func viewFor(_ i : Int) -> some RootView { // 3
// ... your concrete root view constructed here
}
Related
I'm supporting iOS 13 and up. I wish to use the new .toolbar modifier for an optional feature, in devices using iOS 14 and up. I'm using Xcode 13.0 RC 1, build 13A233, but the issue also occurs in Xcode 12.5.1. I have created the following code:
import SwiftUI
struct MyToolbar<T>: ViewModifier where T: View {
let toolbarContent: () -> T
func body(content: Content) -> some View {
if #available(iOS 14.0, *) {
content
.toolbar(content: self.toolbarContent)
}
}
}
extension View {
func myToolbar<T: View>(#ViewBuilder content: #escaping () -> T) -> some View {
self.modifier(MyToolbar(toolbarContent: content))
}
}
struct MyToolbar_Previews: PreviewProvider {
static var previews: some View {
NavigationView {
Text("Hello, world")
.myToolbar {
if #available(iOS 14.0, *) {
Text("Hello, world!")
// ToolbarItem(placement: .bottomBar) {
// Text("Hello, world!")
// }
} else {
EmptyView()
}
}
}
}
}
I have included the preview bit, so the above can be pasted into an empty file in any Xcode SwiftUI project. It works. When I uncomment the ToolbarItem statement, I get the following errors:
Static method 'buildBlock' requires that 'ToolbarItem<Void, Text>' conform to 'View'
Static method 'buildLimitedAvailability' requires that 'ToolbarItem<Void, Text>' conform to 'View'
How can I fix these errors?
I think the main issue is that the .toolbar modifier's block is defined to return something conforming to the ToolbarContent protocol. From the docs:
func toolbar<Content>(content: () -> Content) -> some View where Content : ToolbarContent
As such, within your view modifier
func body(content: Content) -> some View {
if #available(iOS 14.0, *) {
content
.toolbar(content: self.toolbarContent)
}
}
… you need to ensure that self.toolbarContent matches that () -> ToolbarContent type signature.
Just from glancing at your code, I'd be inclined to first try changing your conformance of T from T: View to T: ToolbarContent. By eye that looks like it might be enough, but it's possible you might need to do a bit more work to tidy everything up.
I'm exploring tvOS and I found that Apple offers nice set of templates written using TVML. I'd like to know if a tvOS app that utilises TVML templates can also use UIKit.
Can I mix UIKit and TVMLKit within one app?
I found a thread on Apple Developer Forum but it does not fully answer this question and I am going through documentation to find an answer.
Yes, you can. Displaying TVML templates requires you to use an object that controls the JavaScript Context: TVApplicationController.
var appController: TVApplicationController?
This object has a UINavigationController property associated with it. So whenever you see fit, you can call:
let myViewController = UIViewController()
self.appController?.navigationController.pushViewController(myViewController, animated: true)
This allows you to push a Custom UIKit viewcontroller onto the navigation stack. If you want to go back to TVML Templates, just pop the viewController off of the navigation stack.
If what you would like to know is how to communicate between JavaScript and Swift, here is a method that creates a javascript function called pushMyView()
func createPushMyView(){
//allows us to access the javascript context
appController?.evaluateInJavaScriptContext({(evaluation: JSContext) -> Void in
//this is the block that will be called when javascript calls pushMyView()
let pushMyViewBlock : #convention(block) () -> Void = {
() -> Void in
//pushes a UIKit view controller onto the navigation stack
let myViewController = UIViewController()
self.appController?.navigationController.pushViewController(myViewController, animated: true)
}
//this creates a function in the javascript context called "pushMyView".
//calling pushMyView() in javascript will call the block we created above.
evaluation.setObject(unsafeBitCast(pushMyViewBlock, AnyObject.self), forKeyedSubscript: "pushMyView")
}, completion: {(Bool) -> Void in
//done running the script
})
}
Once you call createPushMyView() in Swift, you are free to call pushMyView() in your javascript code and it will push a view controller onto the stack.
SWIFT 4.1 UPDATE
Just a few simple changes to method names and casting:
appController?.evaluate(inJavaScriptContext: {(evaluation: JSContext) -> Void in
and
evaluation.setObject(unsafeBitCast(pushMyViewBlock, to: AnyObject.self), forKeyedSubscript: "pushMyView" as NSString)
As mentioned in the accepted answer, you can call pretty much any Swift function from within the JavaScript context. Note that, as the name implies, setObject:forKeyedSubscript: will also accept objects (if they conform to a protocol that inherits from JSExport) in addition to blocks, allowing you to access methods and properties on that object. Here's an example
import Foundation
import TVMLKit
// Just an example, use sessionStorage/localStorage JS object to actually accomplish something like this
#objc protocol JSBridgeProtocol : JSExport {
func setValue(value: AnyObject?, forKey key: String)
func valueForKey(key: String) -> AnyObject?
}
class JSBridge: NSObject, JSBridgeProtocol {
var storage: Dictionary<String, String> = [:]
override func setValue(value: AnyObject?, forKey key: String) {
storage[key] = String(value)
}
override func valueForKey(key: String) -> AnyObject? {
return storage[key]
}
}
Then in your app controller:
func appController(appController: TVApplicationController, evaluateAppJavaScriptInContext jsContext: JSContext) {
let bridge:JSBridge = JSBridge();
jsContext.setObject(bridge, forKeyedSubscript:"bridge");
}
Then you can do this in your JS: bridge.setValue(['foo', 'bar'], "baz")
Not only that, but you can override views for existing elements, or define custom elements to use in your markup, and back them with native views:
// Call lines like these before you instantiate your TVApplicationController
TVInterfaceFactory.sharedInterfaceFactory().extendedInterfaceCreator = CustomInterfaceFactory()
// optionally register a custom element. You could use this in your markup as <loadingIndicator></loadingIndicator> or <loadingIndicator /> with optional attributes. LoadingIndicatorElement needs to be a TVViewElement subclass, and there are three functions you can optionally override to trigger JS events or DOM updates
TVElementFactory.registerViewElementClass(LoadingIndicatorElement.self, forElementName: "loadingIndicator")
Quick custom element example:
import Foundation
import TVMLKit
class LoadingIndicatorElement: TVViewElement {
override var elementName: String {
return "loadingIndicator"
}
internal override func resetProperty(resettableProperty: TVElementResettableProperty) {
super.resetProperty(resettableProperty)
}
// API's to dispatch events to JavaScript
internal override func dispatchEventOfType(type: TVElementEventType, canBubble: Bool, cancellable isCancellable: Bool, extraInfo: [String : AnyObject]?, completion: ((Bool, Bool) -> Void)?) {
//super.dispatchEventOfType(type, canBubble: canBubble, cancellable: isCancellable, extraInfo: extraInfo, completion: completion)
}
internal override func dispatchEventWithName(eventName: String, canBubble: Bool, cancellable isCancellable: Bool, extraInfo: [String : AnyObject]?, completion: ((Bool, Bool) -> Void)?) {
//...
}
}
And here's how to set up a custom interface factory:
class CustomInterfaceFactory: TVInterfaceFactory {
let kCustomViewTag = 97142 // unlikely to collide
override func viewForElement(element: TVViewElement, existingView: UIView?) -> UIView? {
if (element.elementName == "title") {
if (existingView != nil) {
return existingView
}
let textElement = (element as! TVTextElement)
if (textElement.attributedText!.length > 0) {
let label = UILabel()
// Configure your label here (this is a good way to set a custom font, for example)...
// You can examine textElement.style or textElement.textStyle to get the element's style properties
label.backgroundColor = UIColor.redColor()
let existingText = NSMutableAttributedString(attributedString: textElement.attributedText!)
label.text = existingText.string
return label
}
} else if element.elementName == "loadingIndicator" {
if (existingView != nil && existingView!.tag == kCustomViewTag) {
return existingView
}
let view = UIImageView(image: UIImage(named: "loading.png"))
return view // Simple example. You could easily use your own UIView subclass
}
return nil // Don't call super, return nil when you don't want to override anything...
}
// Use either this or viewForElement for a given element, not both
override func viewControllerForElement(element: TVViewElement, existingViewController: UIViewController?) -> UIViewController? {
if (element.elementName == "whatever") {
let whateverStoryboard = UIStoryboard(name: "Whatever", bundle: nil)
let viewController = whateverStoryboard.instantiateInitialViewController()
return viewController
}
return nil
}
// Use this to return a valid asset URL for resource:// links for badge/img src (not necessary if the referenced file is included in your bundle)
// I believe you could use this to cache online resources (by replacing resource:// with http(s):// if a corresponding file doesn't exist (then starting an async download/save of the resource before returning the modified URL). Just return a file url for the version on disk if you've already cached it.
override func URLForResource(resourceName: String) -> NSURL? {
return nil
}
}
Unfortunately, view/viewControllerForElement: will not be called for all elements. Some of the existing elements (like collection views) will handle the rendering of their child elements themselves, without involving your interface factory, which means you'll have to override a higher level element, or maybe use a category/swizzling or UIAppearance to get the effect you want.
Finally, as I just implied, you can use UIAppearance to change the way certain built-in views look. Here's the easiest way to change the appearance of your TVML app's tab bar, for example:
// in didFinishLaunching...
UITabBar.appearance().backgroundImage = UIImage()
UITabBar.appearance().backgroundColor = UIColor(white: 0.5, alpha: 1.0)
If you already have a native UIKit app for tvOS, but would like to extend it by using TVMLKit for some part of it, You can.
Use the TVMLKit as a sub app in your native tvOS app. The following app shows how to do this, by retaining the TVApplicationController and present the navigationController from the TVApplicationController. The TVApplicationControllerContext is used to transfer data to the JavaScript app, as the url is transferred here :
class ViewController: UIViewController, TVApplicationControllerDelegate {
// Retain the applicationController
var appController:TVApplicationController?
static let tvBaseURL = "http://localhost:9001/"
static let tvBootURL = "\(ViewController.tvBaseURL)/application.js"
#IBAction func buttonPressed(_ sender: UIButton) {
print("button")
// Use TVMLKit to handle interface
// Get the JS context and send it the url to use in the JS app
let hostedContContext = TVApplicationControllerContext()
if let url = URL(string: ViewController.tvBootURL) {
hostedContContext.javaScriptApplicationURL = url
}
// Save an instance to a new Sub application, the controller already knows what window we are running so pass nil
appController = TVApplicationController(context: hostedContContext, window: nil, delegate: self)
// Get the navigationController of the Sub App and present it
let navc = appController!.navigationController
present(navc, animated: true, completion: nil)
}
Yes. See the TVMLKit Framework, whose docs start with:
The TVMLKit framework enables you to incorporate JavaScript and TVML files in your binary apps to create client-server apps.
From a quick skim of those docs, it looks like you use the various TVWhateverFactory classes to create UIKit views or view controllers from TVML, after which you can insert them into a UIKit app.
I am attempting to present a sheet configuration view (AddSoundEffect) for my main window/view controller (I'm using storyboards), and when the configuration view controller is dismissed, take the values entered in the AddSoundEffect view and pass that back to the main view. My current code in the main view controller:
presentViewControllerAsSheet(self.storyboard!.instantiateControllerWithIdentifier("AddSoundEffect") as! AddSoundViewController
And in the AddSoundViewController.swift file, the code to dismiss it is:
self.dismissViewController(self)
To pass the data, I have a class-independent tuple that I save data to. How do I add a completion handler to presentViewControllerAsSheet, and (optionally) is there a better way to pass the data between view controllers?
Setup: Xcode version 6.4, OS X 10.10.4
Delegation pattern is the easiest way for you.
// Replace this with your tuple or whatever data represents your sound effect
struct SoundEffect {}
protocol AddSoundViewControllerDelegate: class {
func soundViewController(controller: AddSoundViewController, didAddSoundEffect: SoundEffect)
}
//
// Let's say this controller is a modal view controller for adding new sound effects
//
class AddSoundViewController: UIViewController {
weak var delegate: AddSoundViewControllerDelegate?
func done(sender: AnyObject) {
// Dummy sound effect info, replace it with your own data
let soundEffect = SoundEffect()
//
// Call it whenever you would like to inform presenting view controller
// about added sound effect (in case of Done, Add, ... button tapped, do not call it
// when user taps on Cancel to just dismiss AddSoundViewController)
//
self.delegate?.soundViewController(self, didAddSoundEffect: soundEffect)
// Dismiss self
self.dismissViewControllerAnimated(true, completion: {})
}
}
//
// Let's say this controller is main view controller, which contains list of all sound effects,
// with button to add new sound effect via AddSoundViewController
//
class SoundEffectsViewController: UIViewController, AddSoundViewControllerDelegate {
func presentAddSoundEffectController(sender: AnyObject) {
if let addSoundController = self.storyboard?.instantiateViewControllerWithIdentifier("AddSoundEffect") as? AddSoundViewController {
addSoundController.delegate = self
self.presentViewController(addSoundController, animated: true, completion: {})
}
}
func soundViewController(controller: AddSoundViewController, didAddSoundEffect: SoundEffect) {
// This method is called only when new sound effect is added
}
}
Another way is to use closures:
// Replace this with your tuple or whatever data represents your sound effect
struct SoundEffect {}
//
// Let's say this controller is a modal view controller for adding new sound effects
//
class AddSoundViewController: UIViewController {
var completionHandler: ((SoundEffect) -> ())?
func done(sender: AnyObject) {
// Dummy sound effect info, replace it with your own data
let soundEffect = SoundEffect()
//
// Call it whenever you would like to inform presenting view controller
// about added sound effect (in case of Done, Add, ... button tapped, do not call it
// when user taps on Cancel to just dismiss AddSoundViewController)
//
self.completionHandler?(soundEffect)
// Dismiss self
self.dismissViewControllerAnimated(true, completion: {})
}
}
//
// Let's say this controller is main view controller, which contains list of all sound effects,
// with button to add new sound effect via AddSoundViewController
//
class SoundEffectsViewController: UIViewController {
func presentAddSoundEffectController(sender: AnyObject) {
if let addSoundController = self.storyboard?.instantiateViewControllerWithIdentifier("AddSoundEffect") as? AddSoundViewController {
addSoundController.completionHandler = { [weak self] (soundEffect) -> () in
// Called when new sound effect is added
}
self.presentViewController(addSoundController, animated: true, completion: {})
}
}
}
Or many other ways like sending notification, ... Whatever suits your needs. But delegation pattern or closures is the best way to go in this specific case.
I missed that your question is about NSViewController. This example is for iOS, but same pattern can be used on OS X without any issues.
The easiest way to detect sheet opening or closing is to use the Sheet Notifications:
class ViewController: NSViewController, NSWindowDelegate {
override func viewDidLoad(){
NSApplication.sharedApplication().windows.first?.delegate = self
}
func windowDidEndSheet(notification: NSNotification) {
}
func windowWillBeginSheet(notification: NSNotification) {
}
}
I have (from top to bottom) 2 UILabels, 1 UIPickerView, 3 UITexfield, and 1 button. Given the size of the picker, upon the keyboard appearing it overlaps my text fields on the 3.5 and 4 inch devices. I used some code to pop the text fields up when the keyboard shows, but I'm unsure what to do with the picker. I tried hiding it upon keyboard but it's too sudden and the user may want to change their choice which they can't easily. What should I do with the picker given the size limitations?
override func viewDidLoad() {
super.viewDidLoad()
countyPicker.delegate = self
countyPicker.dataSource = self
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name:UIKeyboardWillShowNotification, object: nil);
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name:UIKeyboardWillHideNotification, object: nil);
}
func keyboardWillShow(sender: NSNotification) {
self.view.frame.origin.y -= 150
}
func keyboardWillHide(sender: NSNotification) {
self.view.frame.origin.y += 150
// countyPicker.hidden = true
}
func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
return 1
}
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
return titleData.mdCounties.count
}
func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent componefnt: Int) {
// countyPicker.alpha = 0.3
selectedCounty = titleData.mdCounties[row].name
}
func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
return titleData.mdCounties[row].name!
}
Place the 1 UIPickerView and 3 UITexfield in a single view and pop up the entire view when the keyboard shows up.
As you have already written the code to pop up the text fields it will work out.
Hope this helps you. :)
You could have a simple line indicating the selection of the picker. When the line is tapped, you can show or hide the picker below the line with animation.
It would probably make sense to do this in a UITableView. Look at how Apple shows and hides date pickers in its Calendar app when you edit an event. You can do this very beautifully with standard row animations when inserting and deleting table view rows.
The table view solution is also more flexible as it will always work, even if in the future the number of items that have to be displayed would increase or if Apple introduces the new iPhone nano.
I have been looking for an answer for this, but have only found answers for segues.
I have viewController1 with a button that segues to viewController2. There is no code for this, I set it up through Interface builder. On viewController2 I have a button that dismisses itself with
self.dismissViewControllerAnimated(true, completion, nil)
I want to pass a string from viewController2 back to viewController1 when the view is dismissed. How do I go about doing this? Also, I am using swift.
Thanks in advance!
There are two common patterns, both of which eliminate the need for viewController2 to know explicitly about viewController1 (which is great for maintainability):
Create a delegate protocol for your for viewController2 and set viewController1 as the delegate. Whenever you want to send data back to viewController1, have viewController2 send the "delegate" the data
Setup a closure as a property that allows passing the data. viewController1 would implement that closure on viewController2 when displaying viewController2. Whenever viewController2 has data to pass back, it would call the closure. I feel that this method is more "swift" like.
Here is some example code for #2:
class ViewController2 : UIViewController {
var onDataAvailable : ((data: String) -> ())?
func sendData(data: String) {
// Whenever you want to send data back to viewController1, check
// if the closure is implemented and then call it if it is
self.onDataAvailable?(data: data)
}
}
class ViewController1 : UIViewController {
func doSomethingWithData(data: String) {
// Do something with data
}
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
// When preparing for the segue, have viewController1 provide a closure for
// onDataAvailable
if let viewController = segue.destinationViewController as? ViewController2 {
viewController.onDataAvailable = {[weak self]
(data) in
if let weakSelf = self {
weakSelf.doSomethingWithData(data)
}
}
}
}
}
I used the code from the first answer in a transition between controllers WITHOUT prepareForSegue and worked for me as well.
Here's the sample code.
The First View Controller:
#IBAction func dpAgendaClick(sender:UIBarButtonItem) {
///instantiating view controller with identifier
if let datePickerViewController = storyboard?.instantiateViewControllerWithIdentifier("DatePickerViewController")
as? DatePickerViewController {
///bring instantiated view controller to front
self.presentViewController(datePickerViewController, animated: true, completion: nil)
///wrapping the data returned
datePickerViewController.onDataFiltroAvailable = {[weak self]
(dataFiltro) in
if let weakSelf = self {
///use dataFiltro here
}
}
The second View Controller:
var onDataFiltroAvailable: ((dataFiltro: String) -> ())?
///private var
var dataFiltro: String = ""
///the returning data is obtained on the datePickerChanged event
#IBAction func datePickerChanged(sender: UIDatePicker) {
let dateFormatter = NSDateFormatter()
dateFormatter.dateStyle = NSDateFormatterStyle.ShortStyle
dateFormatter.dateFormat = "yyyy-MM-dd"
dataFiltro = dateFormatter.stringFromDate(datePicker.date)
}
///dismiss the controller on button click
#IBAction func dpOkClick(sender: UIButton) {
///"returning" the data
self.onDataFiltroAvailable?(dataFiltro: dataFiltro)
dismissViewControllerAnimated(true, completion: nil)
}
(Swift 2.1, Xcode 7, iOS9)
If you don't want it to be tightly coupled only between 2 ViewControllers,
You can also use the Notification Design Pattern (Post & Observe), which is mainly used to pass on the same object/information from one VC to multiple View Controllers.
For your scenario :
In VC2.swift :
#IBAction func BackBtn(sender: UIButton) {
NSNotificationCenter.defaultCenter().postNotificationName("ThisIsTheMessage", object: nil, userInfo:["ObjectBeingSent":yourObject])
}
And in VC1.swift :
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("yourFunction:"), name: "ThisIsTheMessage", object: nil)
}
func yourFunction(theNotification : NSNotification) {
if let extractInfo = theNotification.userInfo {
//code to use the object sent from VC2, by extracting the object details
}
}
Common Practise is:
Pass data forward -> Use PrepareForSegue
Pass data backward to the previous View Controller-> Protocol and Delegation
Pass data across multiple View Controllers -> Notifications : Post and Observe(observe in all the View controllers where you are using the object details)