I'm using PNChart in a UIView and overtime my method runs it adds an addition line to the graph rather than recreating the entire graph. How do I clear a UIView, before add[ing]Subview?
#IBOutlet weak var lineChart: UIView!
...
// in function
theLineChart.chartData = [actualData]
theLineChart.strokeChart()
// want to clear self.lineChart here
self.lineChart.addSubview(theLineChart)
If by “clear” you mean remove all previously added subviews from it, you could try something like:
while let subview = lineChart.subviews.last {
subview.removeFromSuperview()
}
The caveat is that lineChart should remain a plain UIView (or your self-made subclass that you know the implementation of), as otherwise it may have internal subviews that you shouldn't remove.
Then again, if it is nothing but a plain UIView, you could simply replace the whole view with a new one (this might even make it simple to cross-fade between old and new views if such is desired).
Related
Recently I wrote an app with one single scene and ViewController. I had to set a custom background picture for the View, which the ViewController manages (i.e. my top view contained the UIImageView). Later on I had to implement some logic in ViewController, so that it properly rotates/changes the picture when the screen is rotated. Also I had to overwrite some properties like preferredStatusBarStyle for the ViewController.
Now I have to implement a couple more scenes / screens in my app and it turns out that they all must have the same design as this currently present screen, so I think it makes sense if I create a CommonViewController which contains this common rotation-related logic for background picture, so that I can inherit all my other ViewControllers from this CommonViewController. The only problem I have is that CommonViewController "requires" that the view it manages has a backgroundPicture: UIView property, which I don't know how to ensure.
If I create a new file CommonViewController together with XIB-file, I can add the backgroundPicture image view in XIB and connect it with code (via regular "control-drag" approach), but apparently this won't work, as there is no guarantee that the views which inherit CommonViewController will have this property. What is the correct way to solve this issue without hacks on iOS in Swift?
Unfortunately I could not find a solution, maybe I've been searching for something wrong. It seems that I somehow need to inherit a CommonViewController for each scene (for each CustomViewController), but also I have to somehow set the top view of each of these controller's to be equal to some CommonView, so that CommonViewController does not crash when I try to access #IBOutlet weak var backgroundPicutre: UIImageView!.
The obvious way would be to define some method or property in the CommonViewController, so that the controllers which inherit it, can implement / override it, but it seems a bit hacky as it still requires copy-pasting in each ViewController which inherits CommonViewController.
How I imagined the solution: I create CustomViewController: CommonViewController, then I create a view controller in my Storyboard and change the "Class" property to "CustomViewController" (in property editor), then I select the view which corresponds to this newly added controller and change the "Class" property to "BackgroundImageView. But I'm not sure if it's the correct way to do (also I doubt thatCustomViewControllerwill properly "connect" itsIBOutletfieldbakcgroundImageViewwith the correspondingUIViewfromBackgroundImageView`, that's why I wanted to ask experts what they think about it.
I think you should define your base controller (CommonViewController) entirely in code, i.e. don't use no xibs / storyboards for the base controller. It doesn't mean you should rid off storyboards / xibs completely. Interface for alll other view controllers except CommonViewController may still be implemented with xibs / storyboards.
In this case CommonViewController implementation may look like this:
import UIKit
class CommonViewController: UIViewController {
// use this property every time you need to
// manipulate backgroundPicture
var backgroundPicture: UIImageView = {
// Replace with your image name
let image = UIImage(named: "BackgroundPicture")!
let imageView = UIImageView()
imageView.image = image
return imageView
}()
override func viewDidLoad() {
// If subclass overrides viewDidLoad()
// it should contain super.viewDidLoad()
super.viewDidLoad()
view.addSubview(backgroundPicture)
// Align backgroundPicture to bounds of superview
// You can remove this code and implement
// your own alignment with frames or Autolayout
backgroundPicture.frame = view.bounds
// Send backgroundPicture to back of the view
// Otherwise backgroundPicture may overlap views added in subclasses
view.sendSubviewToBack(backgroundPicture)
}
override func viewDidLayoutSubviews() {
// If subclass overrides viewDidLayoutSubviews()
// It should contain super.viewDidLayoutSubviews()
super.viewDidLayoutSubvews()
// Align backgroundPicture to bounds of superview
// You can remove this code and implement
// your own alignment with frames or Autolayout
backgroundPicture.frame = view.bounds
}
}
Is it possible to create some sort of generic willSet closure to style IBOutlets in a view controller?
Currently I use this code to set the tint color of UIImageView once its set. ".primary" is a a static variable on UIColor which I created via a UIColor extension:
#IBOutlet weak var someImageView:UIImageView! {
willSet {
newValue.tintColor = .primary
}
}
Now I have a whole bunch of outlets which I want to style in the same way and for me that seems like a lot of duplicated code, especially if I start to apply more styling than just setting the tint so I want something more generic. I came up with:
let tintClosure: (_ newValue: UIView?) -> () = { $0?.tintColor = .primary }
#IBOutlet weak var someImageView:UIImageView! { willSet{ tintClosure(newValue) } }
Now I have to write the code for the actual tinting only once and can just call the closure in willSet. However, I wonder if there is an even more efficient way so I don't even have to call the closure with (newValue) by myself but just giving it the tintClosure.
Like if a function expects a completion handler and you have a function which fits its declaration and you just pass the name of the function instead of a closure in which you call the function.
Something really fancy like:
#IBOutlet weak var someImageView:UIImageView! { superDuperClosure(willSet) }
or
#IBOutlet weak var someImageView:UIImageView! { willSet{ crazyImplementationOfTintClosre } }
or
#IBOutlet weak var someImageView:UIImageView! { willSet.howIsThisEvenPossible }
or
#IBOutlet weak var someImageView:UIImageView! { nowWeAreTalking }
Well, maybe I'm just thinking over the top and I already found the most simplistic way of doing it. Maybe I don't have a deep enough understanding of how willSet works. So dear Swift gurus, teach me how to become a swifty developer.
Update
Based on the second suggestion from Paulo Mattos I had another idea. I created a outlet collection containing all the image views. Then I just iterate over all of them tinting each one with this nice little piece of code:
#IBOutlet var imageViewsToTint: [UIImageView]! { willSet { newValue.forEach { $0.tintColor = .primary } } }
The wonderful thing with this approach is, that you basically can create outlet collection for various purposes like one for tinting, one for text size etc. and then you can just connect the views you want to style to the appropriate collections.
Your solution already feels pretty minimalistc to me :) I can't come up with a shorter hack around that, sorry. This, somewhat exotic, Swift Evolution proposal could provide some help, but it was postponed for now at least.
Let's quickly explore some alternatives beyond willSet (probably gonna be downvoted for this, anyway...):
UIView subclass. I have a UITextField that I use across my app a lot! As such, I implemented a simple subclass and did all styling in there (instead of on each view controller which it appears). Of course, this might not be viable across all your views.
viewDidLoad. You could group all your views in an array and then do the styling inside the viewDidLoad method. Might be more error prone than your current solution — you might miss a view here and there — but gets the job done without too much hacking ;)
I would like to create multiple UIViews that can be reproduced by using a single function. I have a UIView that is placed on a storyboard and connected to my class with an IBOutlet:
#IBOutlet weak var contentView: UIView!
I have a function that loads a xib into my UIView:
func createView(layoutConstant: CGFloat) {
if let customView = NSBundle.mainBundle().loadNibNamed("TestView", owner: self, options: nil).first as? TestView {
contentViewTopLayoutConstraint.constant = layoutConstant
contentView.addSubview(customView)
}
}
I am now trying to add two of them to my view, but only one shows up:
createView(0)
createView(70)
Any ideas?
I think both views are added, although they happen to be in the same spot, so it looks like there is only one! A quick and dirty way to verify that would be updating your createView method with this line:
contentView.frame.origin.y = layoutConstant
Basically your contentViewTopLayoutConstraint is not connected to the views you are creating, so setting its constant value will not have any impact.
Because frames for all those views will of same size. Origin(x,y) will be same for all the views, so they are overlapping one on another and you can only see the top one view.
In your code example it looks like you're only setting a layout constraint on the contentView you are placing your two new views inside of. What you need to do is set layout constraints on the two views your are placing inside in relation to their superview i.e. the contentView.
Basically, add the layout constraints to the customView views.
its quite simple.. iterate a loop by creating uiview along with adding those into the array and customize your particular view by getting them using array index.
Happy code ..
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"
}
I made these (marked with red border) IBOutlets using ctrl + drag
But i don't like to have the exact same line 9 times (DRY)
How do i put these IBOutlets in an Array?
you can define a generic outlet collection in Swift like this:
#IBOutlet var collectionOfViews: Array<UIView>? // = [UIView]?
or for e.g. UIButton objects:
#IBOutlet var collectionOfButtons: Array<UIButton>? // = [UIButton]?
you can find your collections under the Outlet Collections group as usually are in the File's Owner:
it would look on my console after connecting 5 random buttons:
Follow these steps to create an array of outlets an connect it with IB Elements:
Create an array of IBOutlets
Add multiple UIElements (Views) in your Storyboard ViewController interface
Select ViewController (In storyboard) and open connection inspector
There is option 'Outlet Collections' in connection inspector (You will see an array of outlets there)
Connect if with your interface elements
-
class ViewController2: UIViewController {
#IBOutlet var collection:[UIView]!
override func viewDidLoad() {
super.viewDidLoad()
}
}
Solution here Swift - IBOutletCollection equivalent
#IBOutlet var objectCollection: [Object]
This is for macOS (should be similar for iOS) and I do not find an "Outlet Collections" in my storyboard (looks like they took that option out). So I put all my buttons in an NSStackView and linked the stack from storyboard
#IBOutlet weak var buttons: NSStackView!
and then I looped over them to make changes accordingly
for case let (index, button as NSButton) in buttons.arrangedSubviews.enumerated() {
if(index + 1 != someButtonIndex) {button.state = .off}
else {button.state = .on}
}
you can also use tag instead of index
Start with the two view pane where you see both your code and the storyboard. When you make your first IBOutlet connection from the UI to your code, just look carefully at the Connection drop down field and select the option called "Outlet Collection". This will automatically create an array of IBOutlets. Next just look for the little black circle within a circle that is placed in your code where the array is created. Just drag from this circle to all the other UI objects you want to connect to that same collection (not sure if you can mix types). Similarly you can connect all the objects to one Action by dragging from the first black dot created to all the other objects you want to wire up to that action. Also consider EnumerateSequence() to help in working with this Collection. Sweet right?