I'm using storyboards for the first time in iOS 8 and so far have been loving the live rendering aspect of things on the storyboard. However, I seem to have hit a snag in getting my views to render properly on the storyboard.
I have a container UIView that contains a connection to a UILabel on the storyboard, I am attempting to set the label's text based on an IBInspectable attribute on the label's parent container view.
#IBDesignable class ContainerView : UIView {
#IBOutlet weak var : titleLabel : UILabel!
#IBInspectable var title : String = "" {
didSet {
titleLabel?.text = title
}
}
/* Init functions */
prepareForInterfaceBuilder() {
self.titleLabel?.text = title
}
}
If I set the attribute in the storyboard it renders as expected while the program is executing but fails to render in the storyboard as I would expect. I've checked my connections and everything appears to be hooked up properly.
My question is: Is it possible to affect the contents of an IBOutlet connected view via IBInspectable attributes and have them live render on the storyboard, and if so, what am I missing or doing wrong?
Unfortunately you can't see IBOutlet objects in interface builder for your custom views which are marked as IBDesignable. If you want to see your outlets in interface builder, you have to use regular variables instead IBOutlet and you have to create your objects programmatically.
Also please note that, if you need to change something from interface builder for your objects, you have to define your properties as IBInspectable. Currently following variables types are valid for IBInspectable:
Bool, CGFloat, CGPoint, CGRect, CGSize, NSInteger, NSString, UIColor, UIImage
I hope this answer is adequately clear for you.
Edit: I found following article which is describing a way how to do what you need:
http://justabeech.com/2014/07/27/xcode-6-live-rendering-from-nib/
2nd Edit: I tried the article and it works. Now I can see my outlets on interface builder
Related
Using Apple's rather old Swift Getting Started tutorial as a base, I've a working app. I'd like to add a UIView at the top of a table, to appear temporarily if an error occurs. Unfortunately, when trying to access UI elements from the UIView's associated class, I get an "Unexpectedly found nil while implicitly unwrapping an Optional value" error.
https://imgur.com/wfqFach.png
This is actually a UIContainerView, but apparently appears as a UIView.
I've subclassed both the UIView and the linked view (via an embed segue) with a subclass I called ErrorView, and added an #IBOutlet link to the UIView in the table view's subclass. The UI elements are linked to the ErrorView class with an #IBOutlet.
When accessing ErrorView class members via the #IBOutlet in the table subclass, everything is dandy until the ErrorView class tries to access its #IBOutlet linked elements, at which point it crashes with "Unexpectedly found nil while implicitly unwrapping an Optional value."
Strangely, accessing the view itself from within the Error Class is possible, and as such I'm able to do something view-related like change its colour without an error - though the colour change doesn't actually happen.
A very trimmed down version of the code is below, which should reproduce the issue.
I'm using iOS13 and Xcode 11 beta.
ErrorView.swift
import UIKit
class ErrorView: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder: NSCoder) {
super.init(coder: coder)
}
#IBOutlet weak var uiMessage: UILabel!
func setErrorMessage(errorMessage: String){
uiMessage.text=errorMessage //<-- error here
}
}
ModuleTableViewController
import UIKit
import Foundation
class ModuleTableViewController: UITableViewController {
#IBOutlet weak var errorView: ErrorView!
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
errorView.setErrorMessage(errorMessage: "Hello")
}
}
In fact, container views contain View Controller not UIView, you need to set a UIViewController class to your error viewController, then make an outlet for you UIlable, then set a protocol and make you Error View controller conforms to it, when something will happen, it will update the label text.
Dragging a view onto the tableView creates a .tableHeaderView. You could use a UIContainerView holding the view from another view controller, but unless you intend to have a lot going on that would need to be handled that way, you're better off using a simple UIView.
Try it step-by-step:
1) Standard UITableViewController, with your code ready to go (assign the custom class of the controller to TestTableViewController):
2) Add a UIView to the table view. Give it a background color to make it easy to see:
3) Add a UILabel to that view. Give it a background color to make it easy to see. Constrain it 8-pts on all 4 sides:
4) Set the Custom Class of that view to your ErrorView class:
5) Connect the #IBOutlets. Click-drag (not Ctrl) from the circle in the code window to the object. You may find it easier to drag to the object in the Outline pane (so you don't accidentally connect the Label when you're trying to connect the View, for example):
6) It should look like this now (filled-in circles in the code window indicate the outlets have been connected):
7) Run the app, and you should get this:
Let's say I have created a UI with some views using an interface builder (not in code, so not programmatically).
How can I assign human readable ids / tags to these views, so that I could reference them in code?
I know that I can assign an integer tag to a view using attribute inspector and then make a dictionary (or enum) to store the mapping of tags to the views. However, this is an error-prone method which also scales really badly (imaging assigning integer tags to hundred of views in a complex app...).
Is there a better solution for this problem? Is there a way to directly assign a human readable tag / id to a view, like "resumeButton"?
UPDATE:
Here is an example scenario of what I want to achieve:
UI with five different buttons; the buttons have image and no title
all five buttons are connected to the same IBAction in code
in IBAction I have a switch statement, so that depending on which button is clicked, different versions of code are executed
UPDATE 2:
SOLUTION
I ended up implementing a simple custom view:
#IBDesignable
class CustomButton: UIButton {
#IBInspectable var stringTag: String = defaultID
}
This way I can see an additional property stringTag in Interface Builder and can simply add a value to it directly in Interface Builder.
You could create an extension property on UIView to store an identifier string. If you made that extension property IBInspectable, you could set and view it from the storyboard directly.
More detail on setting up such a property in this answer:
https://stackoverflow.com/a/37166043/1830999
The built-in tag property for UIView is just an integer, so it isn't very descriptive for humans who read it.
From what you're describing sounds to me that you are looking for an: Outlets
You are right about tags. Every connection with Interface Builder should be handled using IBAction and IBOutlet.
Since you say that every button has a different action, the simplest solution is to create a separate IBAction for each of them:
#IBAction private func onResumeButtonTapped() {
...
}
#IBAction private func onPauseButtonTapped() {
...
}
If you, for some reason, want to keep them connected to one function, you can use outlets:
#IBOutlet private var resumeButton: UIButton!
#IBOutlet private var pauseButton: UIButton!
#IBAction private func onButtonPressed(_ sender: UIButton) {
switch sender {
case resumeButton:
...
case pauseButton:
...
default:
break
}
}
I'm using UIAppearance a lot for my navigation controllers and other UI objects, and I was wondering if it's possible to have my related objects styled in Interface Builder (maybe with some magic voodoo of #IBDesignable?)
matt's comments on the question are correct. You're able to successfully use UIAppearance proxies in the prepareForInterfaceBuilder method.
Example:
#IBDesignable
class MyCustomView: UIView {
override func prepareForInterfaceBuilder() {
MyCustomView.appearance().backgroundColor = UIColor.redColor()
}
}
This will result in all MyCustomView instances to be rendered red in IB.
I'm writing an app that should present overlays in specific situations, like for example the lack of location services enabled for the app.
Overlay is a UIView with a UIImageView (background) a UILabel (title) and a UIButton calling a specific action. I want to use Interface Builder to set up the overlay UI but I would like to recall the overlay and show it on different UIViewControllers, depending on when the lack of location services is detected.
I have set up a custom class (subclass of UIView) to link a xib file. Code below:
class LaunchCustomScreen: UIView
{
#IBOutlet var title: UILabel!
#IBOutlet var enableLocationButton: UIButton!
#IBOutlet var waitingIndicator: UIActivityIndicatorView!
#IBOutlet var bckgroundImage: UIImageView!
func setupDefault()
{
title.text = "Location Services Required"
enableLocationButton.setTitle("Enable Location Services", forState: UIControlState.Normal)
enableLocationButton.addTarget(self,
action: "promptUserForLocation",
forControlEvents: UIControlEvents.TouchUpInside)
hideLocButton()
}
func hideLocButton()
{
enableLocationButton.hidden = true
}
func showLocButton()
{
enableLocationButton.hidden = false
}
}
Then I have created the xib file which is of Class LaunchCustomScreen and I linked the IBOutlets to all the objects in it (UILabels, UIBUtton, UIImageView)
Then I have set some global functions to be called from any other UIViewController in order to show/hide the overlay on the specific view controller and configure it with UIButton hidden or visible (it will be hidden with a waiting indicator when user location is still loading). Below related code:
func setupLaunchDefault(vc: UIViewController) -> LaunchCustomScreen
{
for aSubview in vc.view.subviews
{
if aSubview.isKindOfClass(LaunchCustomScreen)
{
NSLog("Found already a launch screen. Removing")
aSubview.removeFromSuperview()
}
}
var screen: LaunchCustomScreen = LaunchCustomScreen()
screen.setupDefault()
return screen
}
func showLaunchAskLocation(vc:UIViewController)
{
var screen = setupLaunchDefault(vc)
screen.bounds = vc.view.bounds
screen.showLocButton()
vc.view.addSubview(screen)
}
Now I'm trying if the solution works and it crashes on the setupLaunchDefault function. Reason is that even if an instance of LaunchCustomSCreen is created, the variables (title, enableLocationButton) are still nil. I though they should be non-nil thanks to the IBOutlet to the xib... what am I missing?
Thank you in advance for your help!
I have set up a custom class (subclass of UIView) to link a xib file
No, you haven't. No such "link" is possible.
what am I missing?
You're not missing anything, because you've already figured it out!
Merely creating a LaunchCustomScreen instance out of thin air (i.e. by saying LaunchCustomScreen(), as you are doing) merely creates an instance of this class. It has nothing whatever to do with the .xib (nib) file! There is no magic "link" whatever between the class and the nib! Thus, nothing happens that would cause these properties to get any value. They are, as you have rightly explained, nil.
You have designed and configured one special particular instance of LaunchCustomScreen in the nib. That is the instance whose outlets are hooked up, within the same nib. So if you want an instance of LaunchCustomScreen with hooked-up outlets, you must load the nib! Loading the nib is exactly equivalent to making an instance of what's in the nib - it is a form of instantiation. And here, it's the form of instantiation you want, because this instance is the instance you want.
So, the answer is: do not say LaunchCustomScreen() to get your LaunchCustomScreen instance (screen). Instead, load the nib to get your LaunchCustomScreen instance - and all will be well.
So, let's say your .xib file is called LaunchCustomScreen.xib. You would say:
let arr = NSBundle.mainBundle().loadNibNamed("LaunchCustomScreen", owner: nil, options: nil)
let screen = arr[0] as UIView
The first result, arr, is an array of top-level objects instantiated from the nib. The first of those objects (probably the only member of the array) is the view you are after! So you cast it to a UIView and you are ready to stick it into your interface. Since the view comes from the nib, its outlets are set, which is what you're after. You can do this as many times as you need to, to get as many "copies" of this view as you like.
I am attempting to learn Apple's Swift. I was recently trying to build a GUI app, but I have a question:
How do I interact with GUI elements of my app? For instance, I used interface builder to make a UILabel, and I connected it to my viewcontroller by control-clicking, so that I get the #IBOUTLET thing. Now, how do I, while in my view controller, edit the text of this UILabel? To state it another way, what code can I use to programatically control the text of something on my storyboard? All methods I have found online only appear to work with a button generated in code, not a button generated on a storyboard.
I've seen code like
self.simpleLabel.text = "message"
If this is right, how do I link it with the label in question? In other words, how do I adapt this code to be connected with the IBOutlet (If that's what I do)
If you've successfully linked the control with an IBOutlet on your UIViewController class, then the property is added to it and you would simply replace simpleLabel with whatever you named your IBOutlet connection to be like so:
class MyViewController: UIViewController {
#IBOutlet weak var myLabel: UILabel!
func someFunction() {
self.myLabel.text = "text"
}
}
The outlet you created must've been named by you. The outlet belongs to your view controller. self.simpleLabel means 'fetch the value of my property named 'simpleLabel'.
Since different outlets have different names, using self.simpleLabel here won't work until your outlet is named 'simpleLabel'. Try replacing 'simpleLabel' with the name you gave to the outlet when you created it.
The correct way now would be:
self.yourLabelName.text = "message"
If you have something like this for an IBOutlet:
#IBOutlet var someLabel: UILabel!
then you could set the text property just like in your example:
someLabel.text = "Whatever text"
If you're having problems with this, perhaps you're not assigning the text property in the right place. If it's in a function that doesn't get called, that line won't execute, and the text property won't change. Try overriding the viewDidLoad function, and put the line in there, like this:
override func viewDidLoad() {
super.viewDidLoad()
someLabel.text = "Whatever text"
}
Then, as soon as the view loads, you'll set the text property. If you're not sure if a line of code is executing or not, you can always put a breakpoint there, or add some output. Something like
println("Checkpoint")
inside a block of code you're unsure about could really help you see when and if it runs.
Hope this helps.
You may trying to change a UI component not in the main thread, in that case, do this:
DispatchQueue.main.async {
someLabel.text = "Whatever text"
}