I'm getting really confused about calling methods on a dynamically added subview. I know I'm making a newbie mistake but I just can't figure it out.
My hierarchy looks something like this:
TableView
- TableViewCell
- CustomContainer (UIVIew subclass)
- Widget (UIView subclass)
- myButton
The Widget is added to the CustomContainer via view.addSubview(widget)
I have an #IBAction on myButton that I want to call myFunc declared in the Widget class (below the #IBAction):
#IBAction func myButtonTapped(sender: AnyObject) {
myFunc()
}
...
func myFunc(){
print("myButton was just tapped")
}
When I tap the button I get an error in the console that I can't resolve: [myApp.CustomContainer myButtonTapped:]: unrecognized selector sent to instance
My objective is to have all the methods that relate to the Widget contained in the Widget class or somewhere similar that makes this logical and easy to move around.
I've tried lots of different things but to be honest I'm now just casting around in the dark. If anyone can suggest an approach I'd be very grateful.
Okay, after some quick investigation and a little demo: Add you #IBAction function to your custom UITableViewCell subclass.
When adding the the Widget with the UIButton to the CustomContainer, make sure it's selector is YourCustomUITableViewCellClass.myButtonTapped. Another step you might also want to consider is to refactor your code and maybe not use such a deep hierarchy.
Related
I have a class that defines all styles on a UIVIew.
They are all predefined but I'm not sure when to fire this.
When I try to create an extension for this:
extension UIView
{
func willMoveToSuperview(newSuperview: UIView?)
{
self.stylize() // Another extension somewhere (not here my problem)
}
}
And I'm getting this error:
Method 'willMoveToSuperview' with Objective-C selector conflicts with
previews declaration with the same Objective-c selector
I have tried to override it, but didn't worked either.
Any ideas on how to be able to apply a same behaviour when all of my UIViews will become visible?
You can use Swizzling technic to customize UIView's function. Take a look at:
http://nshipster.com/method-swizzling/ (objective-c)
or
http://nshipster.com/swift-objc-runtime/ (swift)
Hope that helps.
Even though Swift's Extensions are similar to Categories from Objective-C, what you are trying to do is not allowed in Swift.
You cannot override existing functionality:
Extensions can add new functionality to a type, but they cannot override existing functionality.
Source: Swift Extensions - Apple Documentation
Depending on what it is that you are trying to style, you might want to take a look at UIAppearance, it will allow you to style default colors for the UINavigationBar, amongst other things. NSHipster has a good post about it: NSHipster - UIAppearance
You can create a subclass of UIView with the method .stylize().
Then each view you create, you inherit of you UIView subclass.
You'll be able to cal .stylize() on each UIViewSubclass. Simply write the style code inside the subclass and inherite.
Or
Use a category to add the method to the existing UIView class.
See : https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html
Outside of swizzling (not generally recommended), or subclassing as noted by David in his answer, there isn't really a way to override existing methods on a class and its subclasses.
One thing you might try is creating a base class for your view controller instead of all your views. In your view controller base class, you could override viewWillLayoutSubviews to recurse through the view hierarchy and call stylize on each view. This means you would be using the subclass approach in fewer places (just view controllers as opposed to all views).
Another thing you might consider if taking the subclassing approach with UIView is that if you are subclassing anyway, you can take advantage of things like #IBDesignable and #IBInspectable to better integrate those UIView subclasses with storyboards and live preview.
I wrote a Swift library which does exactly this, and it works well for the type of styling it seems you want to do: https://github.com/daniel-hall/Stylish
While trying to implement an extension for UIViewController I realise that there is no normal way, or is not allowed to override this functions (even when they are available for UICollectionViewController and UITableViewController):
extension UIViewController{
public override func viewWillAppear(){
super.viewWillAppear()
//do some stuff
}
}
I realise that there is no normal way, or is not allowed to override this functions (even when they are available for UICollectionViewController and UITableViewController):
viewDidLoad
viewWillLoad
viewWillAppear
viewDidAppear
There is some way to do this? I would like to have some implementation there and working for every UIViewController on my app... All in just one place.
Please, note that I don't want to make a new class subclassing
UIViewController, overriding those methods and making my controller to
extend it. This is the obvious and simplest solution, but this do not satisfy what I'm trying to do.
I'm using swift 1.2 in XCode 6.3
What you are trying to do is similar to what done by this code:
class MyClass {
func myFunc() {}
}
extension MyClass {
override func myFunc() {}
}
The 4 methods that you are trying to override are defined in UIViewController, and not to one of its superclasses. And you can't override a method which is defined in the same class.
Update
I can think of 2 different ways to solve the problem - the first is the one you don't want (subclassing UIViewController).
The other one is method swizzling - I never used it so I don't want to provide you inaccurate info. Maybe it's worth reading this article by Nate Cook, which incidentally is showing an example of replacing viewWillAppear.
I am creating a Swift project and I want to define a specific protocol that enforces other components to implement a animate method:
protocol AnimatableBehavior {
#IBAction func animate()
}
The problem is I want this method to be an IBAction, but I get this error from XCode:
Only instance methods can be declared 'IBAction'
My question is, how would you implement such a thing?
I have considered:
Remove #IBAction, but then I need to remember adding it in every class that implements. Not very elegant and error prone.
Create a base class instead of protocol, but then I am enforcing all components to subclass my base class instead of their own choice ones, so it is not a valid option.
Any other ideas?
EDIT: Response to comments below.
The idea of the IBAction on the protocol is because in the project there will be many different devs implementing small UI components, all of which have the animate method. The components can be added programatically or by Interface Builder and it is very convenient that they are always IBAction because I plan to compose them from IB files to simplify the View Controllers to the maximum extent (and this is clearly a View only task).
Therefore, the solution proposed below of adding a method in the controller that just calls the animate of the component is not good because it is redundant code and makes your Controller more dependent on your View.
The idea of letting the dev to remember adding the IBAction keyword on the method is workable, but as I said it is error prone (and by that I mean that there will be some forgetting about it), and I want to make sure that this is always accessible from IB. It also adds extra cognitive load, because I will need to document this lack of IBAction on the protocol and request the implementor to add it manually.
I know is not the common way of working in iOS and UIKit, but that was why I posted the question, maybe someone has an alternative idea.
It doesn't make any sense to have an #IBAction in a protocol. #IBAction is nothing more than a keyword for Interface Builder to have a hook when you're control+dragging from Interface Builder to your actual source code.
This is just a simple misunderstanding of what #IBAction actually is and does.
A method does not have to be marked as #IBAction in order for it to be the target of a UI element's actions. You programmatically hook up any method to any action using the addTarget set of methods that UI elements have. The method does not have to be marked as an #IBAction to do this.
Regardless of whether or not a protocol defines a method as #IBAction, the class conforming to the protocol can add it (and still be conforming to the protocol.
protocol FooProtocol {
func doSomething()
}
class ViewControllerA: UIViewController, FooProtocol {
#IBAction func doSomething() {
// do something
}
}
class ViewControllerB: UIViewController, FooProtocol {
func doSomething() {
// do something
}
}
Both of these view controller subclasses conform to the protocol, and having #IBAction there is ONLY necessary if you intend to hook up an action from interface builder!
Ultimately, whatever you're trying to do, if you think an #IBAction is necessary in your protocol, I think you're taking the wrong approach to something. It's hard to say what the right approach would be without knowing more details about what you're actually doing, but it never makes sense for #IBAction to belong in a protocol.
To me, it seems like the methods your protocol enforces shouldn't at all be tied to #IBAction methods. Instead, whatever user interaction should trigger the animation, should in turn call the animate method. For example, if we weren't talking about the protocol, my recommendation would be this sort of set up:
class ViewController: UIViewController {
#IBAction func buttonThatStartsAnimation {
self.animate()
}
func animate {
// code that does all the animation
}
}
So, with the protocol, we should take the same seperation of duties between the method that's actually initiating the animation code (which in the case of protocols, this is obviously some other outside class), and the animate method should only ever handle doing the relevant animations.
Importantly, just as a general rule, you shouldn't be directly referring to your #IBAction methods or your #IBOutlet variables directly from outside the class which defines them.
I totally agree with OP, although until Swift 3.1 you can't really declare anything as #IBOutlet, #IBAction, #objc etc in a protocol. As a workaround, I chose to build something based on pod 'ActionKit' and wrote something like:
protocol RequiresAnimation {
var animateButton: UIButton! { get }
func enableAnimateButton()
func actionAnimate()
}
extension RequiresAnimation where Self: UIViewController {
func enableAnimateButton() {
animateButton.addControlEvent(.touchUpInside) {
self.actionAnimate()
}
}
func actionAnimate() {
// animate here
}
}
And make your view controller:
class MyViewController: UIViewController, RequiresAnimation {
#IBOutlet var animateButton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
enableAnimateButton()
}
}
I wish there would be any easier approach, but so far you make need to do these 2 things manually: declaring your button as #IBOutlet and call a setup function. The reason why we need to import ActionKit is that we can't addTarget in protocol extension.
So I'm trying out Xamarin Forms, and I made a control that has a renderer that outputs a UICollectionView. The collection view in question was ported from an Objective C version. In the Objective C version, I implemented collectionView:didSelectItemAtIndexPath: and when I clicked on the item that method was called. But in the Xamarin version, this does not seem to be the case and the ItemSelected method is not called. I've tried using both the Delegate and WeakDelegate versions to no avail. I made sure AllowsSelection is true.
I tried adding a UIButton to the cell, and was able to get a log entry from its TouchUpInside handler, so I don't think it's a matter of another view on top stealing the touches. Pans and such work. And in Simulator I had it highlight the drawn layers and didn't notice anything fishy.
Anyone have any ideas of stuff to try? Thanks.
I don't know if this can help you, but i get the same problem using the GridView control of the Xamarin.Forms.Labs.
I see that in delegate, the method "ItemSelected" is not called, but is call the "ItemHighlighted" method. So I used this to make the GridView selectitem works.
I hope this can be helpfull. :)
Double check that you have assigned the UICollectionViewSource object to ColelctionView.Source and NOT ColelctionView.DataSource by mistake
I did eventually fix this. What was happening is that Xamarin.Forms adds a gesture recognizer to the root of the page which cancels touches in the page. This works well in general, but does not work well in the case of UICollectionViews where it interferes with the UICollectionView calling ItemSelected.
What I ended up doing was to create this custom renderer:
public class IosTapFixPageRenderer : PageRenderer {
public override void ViewDidLoad()
{
base.ViewDidLoad();
foreach (var g in View.GestureRecognizers) {
g.CancelsTouchesInView = false;
}
}
}
Then I assigned this as the renderer for problem pages containing UICollectionViews using the usual attribute method:
[assembly: ExportRenderer(typeof(CalendarPage), typeof(IosTapFixPageRenderer))]
I am having difficulties wrapping my head around this. I have a MyCollectionViewController class that has a method called 'someMethod'. I also have MySupplementaryView class that has a button called 'aButton'. The SupplementaryView is a footer in the UICollectionView.
How can I get the IBAction for aButton to call someMethod?
Thanks in advance for your response.
I think I found it.
[delegate someMethod];
Silly me.