First of all I have to say I am really new to swift and Objective C.I am learning them by myself.
I have a question for this code
I have a delegate in my SettingViewController called "settingsViewControllerFinished" and it pass the whole controller as a variable.
the code like this:
in my SettingViewController.swift
protocol SettingViewControllerDelegate: class {
func settingsViewControllerFinished(settingsViewController: SettingsViewController)
}
#IBAction func close(sender: AnyObject) {
dismissViewControllerAnimated(true, completion: nil)
self.delegate?.settingsViewControllerFinished(self)
}
I am confused.What did you mean if you pass the whole controller as a variable?(maybe the question is silly for you)
in my viewController:
func settingsViewControllerFinished(settingsViewController: SettingsViewController)
{
self.brushWidth = settingsViewController.brush
self.opacity = settingsViewController.opacity
self.red = settingsViewController.red
self.green = settingsViewController.green
self.blue = settingsViewController.blue
}
I guess the reason is:I pass everything in SettingViewController to ViewController so that I could use the variables in SettingViewController.
Am I rihgt?
Generally you are correct, yes: passing the SettingViewController back to its delegate enables the original caller to not have to keep a reference to the created and shown SettingViewController since the delegate method sends the relevant information along already.
But there is more: In some cases of delegates this style is useful for something different. Imagine a click handler consisting of a function func somethingGotClicked(sender:YourSenderType). If your class creates multiple instances of YourSenderType and shows them at the same time registering itself as their delegate there would be no way to know which one got clicked if there was no sender parameter. In some func somethingGotClicked() you would not know which one got clicked. That capability is often needed when showing multiple UITableView or UICollectionView is one single view with one single instances set as their delegate.
Related
I have a separate class which when called upon updates the ToolTip (a text property) for an NSButton in a pistonViewController via its IBOutlet.
However, whenever I try to perform the action, I get the error
"Unexpectedly found nil while implicitly unwrapping an Optional value"
since pistonViewController.piston.tooltip didn't work, I created an instance above the class:
let pistonView = pistonViewController();
and then from within the separate class called pistonView.set_piston();
func set_piston(index: Int) {
piston1.toolTip = "yay it worked!";
}
I get the same error: found nil.
How to get the correct instance of the pistonViewController (the one that appears on viewDidLoad) so that piston1 will not be nil?
There is this solution, but it looks needlessly complex. This one appears to only work on iOS, using a storyboard.InstantiateViewController command that does not work on MacOS. This MacOS solution is poorly explained and does not appear to work.
"[How do I] Modify IBOutlet property from outside of viewDidLoad"
(But what you're really asking is how you modify a view controller's views from outside of the view controller.)
The short answer is "Don't do that." It violates the principle of encapsulation. You should treat a view controller's view properties as private, and only modify them inside the view controller's code.
(To misquote Groucho Marx: "Doc, it crashes when I do this". "Then don't do that!")
Instead, add a public property (pistonToolTip) in your PistonViewController (Class names should begin with upper-case letters).
class PistonViewController: UIViewController {
var pistonToolTip: String {
didSet {
piston?.tooltip = pistonToolTip
}
}
}
And in case you set pistonToolTip before your PistonViewController has loaded its views, add this line to viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
piston?.tooltip = pistonToolTip
// The rest of your viewDidLoad code
}
Ultimately I just set it up in viewDidLoad, with a timer waiting for the other program to get the variables that will then be assigned to the pistons.
The lack of effective pointers to instances of View Controllers makes anything else not possible or perhaps just arcane and difficult.
I am quite new into programming and facing some issues while trying to slim down my ViewController by moving creation of the tableView and associated views to the separate class and moving delegates and datasource from VC to separate one.
My constellation of current files and work is as follows:
After network connection, when data are received, I am calling inside a closure class to set view which will have embedded UITableView.
Fetched data are being saved into the CoreData stack
I instantiate view from another class
var detailView: DetailView! { return self.view as? DetailView }
Once I will download first part of the UI (separate call which works fine)
I am moving onto the part which is messy and surpass my abilities
I call a function createReposCard()
dispatchGroup.notify(queue: dispatchQueue) {
DispatchQueue.main.async {
// slide animation
UIView.animate(withDuration: 0.75, delay: 0.5, usingSpringWithDamping: 0.9, initialSpringVelocity: 0.0, options: [], animations: {
self.detailView.reposCard.center = CGPoint(x: self.detailView.reposCard.center.x, y: self.detailView.reposCard.center.y-UIScreen.main.bounds.height)
}, completion: nil)
self.detailView.createReposCard(for: self.repos)
self.detailView.detailsTableView.reloadData()
self.activityIndicator.stopAnimating()
self.activityIndicator.removeFromSuperview()
}
}
Code is incomplete to depict the problem only, but what it does one by one.
I am passing info about selected user (irrelevant info)
then I am making a reference to my DetailsViewController which still e.g. holds CoreData stack
In initializer I am instantiating detailsViewController and passing it onto the class which holds delegates (I am passing it to have there reference to the CoreData)
class DetailView: UIView {
var selectedUser: User?
var detailsViewController: DetailsViewController!
let detailsTableView: UITableView = {
let tableView = UITableView()
tableView.frame = CGRect.zero
tableView.register(UITableViewCell.self, forCellReuseIdentifier: "reposCell")
return tableView
}()
init(selectedUser:User, frame: CGRect) {
super.init(frame: frame)
self.selectedUser = selectedUser
detailsViewController = DetailsViewController()
let tableViewDelegates = TableViewDelegates(detailsViewController: detailsViewController)
detailsTableView.delegate = tableViewDelegates
detailsTableView.dataSource = tableViewDelegates
}
And finally code jumps into the depicted class where I am knocked down by "Unexpectedly found nil while implicitly unwrapping..."
public class TableViewDelegates: NSObject, UITableViewDataSource,UITableViewDelegate {
private let detailsViewController: DetailsViewController
init(detailsViewController: DetailsViewController){
self.detailsViewController = detailsViewController
super.init()
}
public func numberOfSections(in tableView: UITableView) -> Int {
return detailsViewController.fetchedResultsController.sections?.count ?? 1
}
...
Actually I don't know if my concept is good as I feel quite lost, but my intentions were as follows:
Move View creation to other class
Move TableView delegates to other class
Finally - move networking and CoreData to other class.
But as I see, simple data passing is overcoming my abilities.
I think this question can be divided into two parts:
1) Why is my variable nil when I unwrap it?
I don't think we have enough information to answer this accurately, but my overall approach would be like this:
Check what nil variable is being unwrapped;
Make sure this variable is being properly initialized;
Make sure that the object is not being incorrectly deinitialized;
If you're using Storyboard, use the inspectors to check if everything is set correctly.
There's a particular observation about step 2: you should check the order of execution of your methods to make sure that the variable is properly initialized. Why am I emphasizing this? Because there's a chance that some view (e.g., detailView) is initialized like an ordinary UIView, and then you try to access an element that is not part of a UIView object (e.g., a table view). In other words, check if you're setting the custom views before you try to access them.
2) How to structure the project in a more organized way?
This is a more interesting question, and I think that choosing a better approach will help you to avoid issues like what you're experiencing. I will divide this into some topics. Everything here is my personal opinion and doesn't necessarily reflect the best approach, especially because "best" is subjective here.
PersistenceManager class
First, passing a reference of a view controller to another class just to access CoreData doesn't seem like a good option. A better approach would be to have a PersistenceManager class, for example. You could use an object of this class to fetch and save data. You could pass this object instead of the view controller.
In some architectures (e.g., VIPER), it wouldn't be correct for the view controller to access the persistence directly, so it would be more appropriate to pass an array of already fetched objects. For example:
class TableViewController {
private let tableView: UITableView!
private var currentlyDisplayedUsers: [Users]?
func displayUsers(_ users: [Users]) {
self.currentlyDisplayedUsers = users
self.tableView.reloadData()
}
}
In the example above, the tableView would display currentlyDisplayedUsers, which would be updated by the method displayUsers, which would be called by someone else, like a Presenter.
Network class
Second, I think you should have a network class to download data from the internet. You would use instances of the Network class in the application logic. In other words, you would have something like
// This is in the application logic
// In MVC, the logic is in the Controller, while in VIPER the logic is in the Interactor
class ApplicationLogic {
let networkAPI: Network?
...
func fetchUserData() {
networkAPI?.fetchUsers() { data, error in
// Update the UI based on the response
// Using the previous example, you could call displayUsers here
}
}
}
TableView, TableViewDelegate, and TableViewDataSource
Finally, how to organize these guys. UITableViewDelegate is responsible for telling us about events in the table, while UITableViewDataSource is responsible for filling the table with data, which means that both are strongly related to the table view itself. That said, imho, both should be implemented in different swift files, but as extensions of the view controller that has a reference to the table view. Something like
// TableViewController+UITableViewDelegate.swift
extension TableViewController: UITableViewDelegate {
...
}
// TableViewController+UITableViewDataSource.swift
extension TableViewController: UITableViewDataSource {
...
}
Using this approach, the delegate and the data source would have access to the users array, mentioned earlier. Here is an example of how to implement a similar approach using VIPER.
So, I hope I could provide a basic idea on these topics. If you want to understand more about how to structure your code, I suggest researching iOS design patterns and architectural patterns. Some architectural design patterns that are famous in iOS development are MVC, MVP, MVVM, and VIPER.
I am fairly new at coding in swift and I've been trying to find a solution to my problem for the past couple days, and am not able to.
I have a class named userData with various properties:
class UserData {
var name: String
var age: Int
var credits: Int = 1
...
init(name: String, age: Int) {
self.name = name
self.age = age
}
}
Inside the viewController.swift I have declared an object of this class:
...
var user = UserData(name: "testing", age: 5)
...
Inside the same viewController I have a UITableView with a few UITableViewCells. In every cell there is a UIStepper
Using the UIStepper from a cell I want to increment or decrement the property credits of my object user that sits inside the viewController.swift, and do that from within the tableViewCell.swift file
From what I can find, I think I should use a delegate but I can figure out how to implement it.
More information:
Pardon the art work, I am not an artist...
The user has a set amount of ants available to work (this number is a property of my object user). There is also a property for the amount of ants currently working ('ants used' in my screen shot).
At first, the white label on top says '0/5' (Meaning the user has 5 available ants to work but none are currently working).
When the user increments the stepper for 'scavenger ants', the white label on top should say '1/5' (Meaning that there is currently 1 ant working out of 5 that are available).
What I want to do, is that when the user clicks on a stepper, the user's property for the 'ants currently working' increments or decrements appropriately.
Thank you
Set that logic up in the view controllers' cellForRowAt.
When setting up the cell, you can add a function inside your view controller as the target every-time the UIStepper value changes:
// inside cellForRowAtIndexPath:
cell.addTarget(self, action: #selector(doSomething(sender:), for: .valueChanged)
Inside doSomething you set up the logic for updating your model.
func doSomething(sender: UIStepper) {
// do stuff here
}
Edit with an example of the delegate pattern which would be a better solution, for future readers.
First create a protocol:
protocol StepperCellDelegate {
func didChangeValueForStepper(inCell: Cell, whateverInfoYouWantHere:...)
func otherUsefulFunctions(...)
}
In your cell class, set a target/action for when your value is changed:
// inside the cell's initialization (`init(style:reuseIdentifier:)`
self.addTarget(self, action: #selector(valueChanged(sender:), for: .valueChanged)
Your cell also needs a delegate property:
weak var stepperCellDelegate: StepperCellDelegate?
doSomething would look something like this:
func valueChanged(sender: UIStepper) {
stepperCellDelegate?.didChangeValueForStepper(inCell: self, ...)
}
Your ViewController will implement the protocol
extension MyViewController: StepperCellDelegate {
func didChangeValueForStepper(inCell: Cell, whateverInfoYouWantHere:...) {
// implementation here
}
func otherUsefulFunctions(...){
// implementation here
}
}
And inside cellForRowAtIndexPath set itself as the delegate:
// inside cellForRowAtIndexPath:
cell.stepperCellDelegate = self
Delegation is the proper way of handling this.
That UItableviewCell — both appear to be similar —
should expose a protocol with a set of methods
that the UIViewController can implement. Methods are
triggered when you tap on the UIStepper widget.
Best to stick to this methodology, and reuse it everywhere. Makes
things manageable loosely coupled.
Description
I am trying to use NSSegmentedControls to transition between Child ViewControllers. The ParentViewController is located in Main.storyboard and the ChildViewControllers are located in Assistant.storyboard. Each ChildViewController has a SegmentedControl divided into 2 Segments and their primary use is to navigate between the ChildViewControllers. So they are set up as momentaryPushIn rather than selectOne. Each ChildViewController uses a Delegate to communicate with the ParentViewController.
So in the ParentViewController I added the ChildViewControllers as following:
/// The View of the ParentViewController configured as NSVisualEffectView
#IBOutlet var visualEffectView: NSVisualEffectView!
var assistantChilds: [NSViewController] {
get { return [NSViewController]() }
set(newValue) {
for child in newValue { self.addChild(child) }
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Do view setup here.
addAssistantViewControllersToChildrenArray()
}
override func viewWillAppear() {
visualEffectView.addSubview(self.children[0].view)
self.children[0].view.frame = self.view.bounds
}
private func addAssistantViewControllersToChildrenArray() -> Void {
let storyboard = NSStoryboard.init(name: "Assistant", bundle: nil)
let exampleChild = storyboard.instantiateController(withIdentifier: "ExampleChild") as! ExampleChildViewController
let exampleSibling = storyboard.instantiateController(withIdentifier: "ExampleSibling") as! ExampleSiblingViewController
exampleChild.navigationDelegate = self
exampleSibling.navigationDelegate = self
assistantChilds = [exampleChild, exampleSibling]
}
So far so good. The ExampleChildViewController has an NSTextField instance. While I am in the scope of the TextField, I can trigger the action of the SegmentedControls. Its navigating forward and backward as it should. But once I leave the scope of the TextField I can still click the Segments, but they are not triggering any action. They should be able to navigate forward and backward even if the TextField is not the current "First Responder" of the application. I think I am missing something out here, I hope anyone can help me with this. I know the problem is not the NSSegmentedControl because I am seeing the same behavior with an NSButton, which is configured as Switch/Checkbox, in the SiblingViewController. I just don't have any idea anymore what I am doing wrong.
It`s my first time asking a question myself here, so I hope the way I am doing is fine for making progress with the solution. Let me know if I can do something better/different or if I need to provide more information about something.
Thanks in advance!
Additional Information
For the sake of completeness:
The ParentViewController itself is embedded in a ContainerView,
which is owned by the RootViewController. I can't imagine this does
matter in any way, but this way we are not missing something out.
I am actually not showing the navigation action, because I want to
keep it as simple as possible. Furthermore the action is not problem,
it does what I want it to do. Correct me if I am wrong with this.
Possible solutions I found while researching, which did not work for me:
Setting window.delegate of the ChildViewControllers to NSApp.windows.first?.delegate
Setting the ChildViewController to becomeFirstResponder in its func viewWillAppear()
visualEffectView.addSubview(self.children[0].view, positioned: NSWindow.OrderingMode.above, relativeTo: nil)
Related problems/topics I found while researching:
Basic segmented control not working
Adding and Removing Child View Controllers
NSSegmentedControl - Odd appearance when placed in blur view
How to set first responder to NSTextView in Swift?
How to use #selector in Swift 2.2 for the first responder
Accessing methods, actions and/or outlets from other controllers with swift
How to use Child View Controllers in Swift 4.0 programmatically
Container View Controllers
issues with container view
Control a NSTabViewController from parent View
How to detect when NSTextField has the focus or is it`s content selected cocoa
SOLUTION
let parentViewControllerInstance = self.parent as! ParentViewController
segmentedControl.target = parentViewControllerInstance
In my case I just had to set the delegate as the target of the sendAction method.
Background
Ok, after hours of reading the AppKit Documentation I am now able to answer my own question.
First, debugging the UI showed that the problem was definitely not in the ViewHierarchy.
So I tried to think about the nature of NSButton and NSSegmentedControl. At some point I noticed that both are subclasses of NSControl.
class NSSegmentedControl : NSControl
class NSButton : NSControl
The AppKit Documentation says:
Discussion
Buttons are a standard control used to initiate actions within your app. You can configure buttons with many different visual styles, but the behavior is the same. When clicked, a button calls the action method of its associated target object. (...) You use the action method to perform your app-specific tasks.
The bold text points to the key of the solution – of its associated target object. Typically I define the action of an control item like this:
button.action = #selector(someFunc(_:))
This causes the NSControl instance to call this:
func sendAction(_ action: Selector?, to target: Any?) -> Bool
Parameter Description from the documentation:
Parameters
theAction
The selector to invoke on the target. If the selector is NULL, no message is sent.
theTarget
The target object to receive the message. If the object is nil, the application searches the responder chain for an object capable of handling the message. For more information on dispatching actions, see the class description for NSActionCell.
In conclusion the NSControl instance, which was firing the action method (in my case the NSSegmentedControl), had no target to send its action to. So it was only able to send its action method across the responder chain - which obviously has been nil while the first responder was located in another view.
I have a document window that contains a number of NSView subclasses, switched between using a tab control. Each of the subclasses, and the window's ViewController, support different user actions accessed through menu items tied to the First Responder.
I'd like to perform a segue from one of those views in response to a menu item. However, NSView does not support performSegueWithIdentifier, it appears to be something that is part of NSViewController alone.
Can someone suggest a way around this? I have seen suggestions to pass the VC into the views, but I am not clear how to do that. Or perhaps there is a better way?
view.containingController.performSegue()
note: you have to add containingController to your views
I WOULD add the viewController to the responder chain and then make containingController a computed property in an extension!
e.g. add vc as responder:
override func awakeFromNib() {
super.awakeFromNib()
self.nextResponder = self.view
for subview in self.view.subviews {
subview.nextResponder = self
}
}
e.g. containingController in extension
extension NSView {
var containingController: NSViewController? {
get {
while(self.nextResponder != nil) {
if(self.nextResponder is NSViewController) {
return self.nextResponder
}
}
return nil
}
}
}
You could do that (see Daij-Djan's answer), however it is not what I would recommend, since a hypothetical programmer who will be using your code, but is not familiar with it (let's say, you in a year :) ) might be caught by surprise by such behaviour.
I would recommend you to add a delegate (conforming to your custom protocol, let's call it MyViewDelegate) to your NSView with a method like viewRequiresToPerformTransition(view: YourViewSubclass). Then you implement this method (more generally, you conform to MyViewDelegate protocol) in your view controller and inside its implementation perform any segue you want.