When should I use anyObject insted of UIButton in swift?
I am making an IBAction for my button that will be used to do more than on task on of the tasks is to switch to the next view.
Ultimately, it really doesn't matter.
You can choose to use the parameter of (sender: AnyObject) or you can use (sender: UIButton).
There might be times however where you might have to cast AnyObject as a UIButton if you need access to the properties provided by UIButton.
For example let's say you have and you want the button to disappear after it is clicked.
func doSomething(sender: AnyObject) {
let button: UIButton = sender as! UIButton
button.hidden = true
}
The purpose of using an abstract AnyObject type for an IBAction may be advantage for a situation in which you have multiple UI objects that should trigger the same action. An example of this would be if you wanted to have a button and a gesture recognizer share the functionality of a common action. Even with a shared action, it would be possible to have different execution paths for the two objects.
Related
I am trying to implement a xylophone where I want to play different sounds on tap of different buttons which I merged it to one IBAction function and have differentiated with different tags.
#IBAction func keysPressed(_ sender: UIButton) {
}
I am importing AVFoundation but not getting the exact function to call to play sounds
I need a function which I can call in each If else statement differentiating buttons with tags to play sounds.
Assuming this is a question on how to get different buttons to play different sounds, you could subclass UIButton to include a field for tracking which note it is, and call the correct function based on that.
class XyloKey: UIButton {
var note: String
}
And then in your view controller:
let key = XyloKey()
key.note = "C5"
key.addTarget(self, action: #selector(playNote(_:)), for: .touchUpInside)
And assuming you name your files by note name (e.g. "note_C5.mp3").
func playNote(_ sender: XyloKey) {
let url = NSBundle.mainBundle().URLForResource("note_\(sender.note)", withExtension: "mp3")
playSound(url)
}
Where playSound plays the sound of the passed file. See the link passed in the flag above for details.
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 have an app with some buttons, when those buttons are pressed the image on them should change. I assume that the TouchUpInside runs when you tap and remove the finger while still holding inside the area of the element, however it only works rarely and I'm not sure why.
The reason I use TouchUpInside instead of TouchDown is because I want the user to be able to cancel the action.
I'm sorry if I've misunderstood anything about those events and if this has already been asked. I couldn't find an answer to my problem searching the web.
//The IBAction is set to trigger on TouchUpInside
#IBAction func action11(sender: UIButton) {
setTile(sender)
}
func setTile(sender: UIButton) {
if turn {
print("O's turn")
sender.setImage(xTile, forState: .Normal)
turn = false
}
}
EDIT: Added the necessary code
There are some properties of UIButtons which you can use to achieve what you want.
You can use Default and selected state of uibutton to set two different images.
In XIB select state "Default" and assign default image to that state again select state to "Selected" and assign image which you want after button section.
and add following line in button selection method.
-(IBAction)buttonTapped:(UIButton *)sender{
sender.selected = !sender.selected;
}
Your understanding is correct, you need to use touchUpInside.
I assume you are trying to create a button that has a toggle function. On one touch you want the button to have the value Say "X" and when touched again the button has a value "O".
Take a look at this code below, this should do the job.
class ViewController: UIViewController {
var isButtonPressed = false{
// Adding a Property Observer, that reacts to changes in button state
didSet{
if isButtonPressed{
// Set the Value to X.
}else{
// Set the Value to O.
}
}
}
#IBAction func changeButtonValue(sender: UIButton) {
// Toggle the button value.
isButtonPressed = !isButtonPressed
}
}
If you don't set turn=true after the first time, this code is executed it will be executed only one.
if turn {
print("O's turn")
sender.setImage(xTile, forState: .Normal)
turn = false
}
Check if the button frame is large enough to get finger touch.
Apple says at least 35x35 pixel.
I am building an app for keeping track of reading assignments for a university course. Each ReadingAssignment has included a Bool value that indicates if the reader has finished reading the assignment. The ReadingAssignments are collected into WeeklyAssignment arrays. I want to have the user be able to touch a label and have a checkmark appear and show the assignment as completed. I would like this touch to also update the .checked property to true so I can persist the data.
So, I am trying to have the gestureRecognizer call the labelTicked() method. This works and prints to the console. However, when I try to pass in the assignment parameter, it compiles, but crashes on the touch with an "unrecognized selector" error. I have read every topic i can find here, and haven't found the solution. They all say ":" signifies a Selector with parameters, but still no go.
Can you see what I am doing wrong?
func configureCheckmark(cell: UITableViewCell, withWeeklyAssignment assignment: WeeklyAssignment) {
let checkLabel = cell.viewWithTag(1002) as! UILabel
checkLabel.userInteractionEnabled = true
let gestureRecognizer = UITapGestureRecognizer(target: self, action: Selector("labelTicked:assignment"))
checkLabel.addGestureRecognizer(gestureRecognizer)
}
#objc func labelTicked(assignment: WeeklyAssignment) {
assignment.toggleCheckmark()
if assignment.checked {
label.text = "✔︎"
} else {
label.text = ""
}
}
I would also love to pass in the UILabel checkLabel so I can update it in the labelTicked() method.
Thanks for your help.
There are two distinct problems here:
The syntax for the selector is wrong; the : doesn't mark the beginning of a parameters part, it merely marks that this function takes parameters at all. So the tap recognizer should be initialized as UITapGestureRecognizer(target: self, action: "labelTicked:"). Easy fix. That is the good news.
The bad news: even with perfect syntax it will not work the way you set it up here. Your tap recognizer cannot pass a WeeklyAssignment object as a parameter. In fact, it cannot pass any custom parameter at all. At least, not like that.
However, you can pass it in the sender (which is usually the view the gesture recognizer is attached to). You can grab it by changing your method to
func labelTicked(sender: AnyObject) {
(note that AnyObject may be declared as a more specific type if you know exactly what to expect.)
Going through the sender, you could now theoretically infer which label it is that has been tapped, which data entity that labels corresponds to, and which state the checked property of that entity is in. I think this would become very convoluted very quickly.
Seemingly straightforward things becoming convoluted is usually a good sign that we should take a step back and look for a better solution.
I'd suggest dropping the whole GestureRecognizer approach at this point, and instead exploit the fact that each cell in a table view already comes with its own "tap recongizing" functionality out of the box: the didSelectRowAtIndexPath: method of the table view's delegate. There, you can easily use the supplied NSIndexPath to retrieve the corresponding model entity from the data source to read and modify its parameters as you see fit. Via cellForRowAtIndexPath: you can then get a reference to the correct cell and change its contents accordingly.
Update for Swift 3:
As the Swift language evolves and using String-based selectors (e.g. "labelTicked:") is now flagged as deprecated, I think it's appropriate to provide a small update to the answer.
Using more modern syntax, you could declare your function like this:
#objc func labelTicked(withSender sender: AnyObject) {
and initialize your gesture recognizer like this, using #selector:
UITapGestureRecognizer(target: self, action: #selector(labelTicked(withSender:)))
The correct selector for that function is labelTicked:. Furthermore, you can use a string directly as a selector. Thus:
let gestureRecognizer = UITapGestureRecognizer(target: self, action: "labelTicked:")
But you can't arrange to pass an arbitrary object along to the method when the recognizer fires. A better way to do this is to create a subclass of UITableViewCell. Let's call it AssignmentCell. Give the subclass an assignment property, and move the labelTicked: method to AssignmentCell.
If you've designed the cell in your storyboard, you can add a tap recognizer to the label right in the storyboard, and wire the recognizer to the cell's labelTicked: method in the storyboard.
In your table view data source's tableView(_:cellForRowAtIndexPath:), after you've dequeued the cell, set its assignment property to the assignment for that row.
I have a custom UIView (called GridView) that I initialize and then add to a ViewController (DetailViewController). GridView contains several UIButtons and I would like to know in DetailViewController when those buttons are touched. I'm new to Swift and am wondering what is the best pattern to use to get those events?
If you want to do this with notifications, use 1:
func postNotificationName(_ notificationName: String,
object notificationSender: AnyObject?)
in the method that is triggered by your button. Then, in your DetailViewController, add a listener when it is initialized with 2:
func addObserver(_ notificationObserver: AnyObject,
selector notificationSelector: Selector,
name notificationName: String?,
object notificationSender: AnyObject?)
Both functions can be called from NSNotificationCenter.defaultCenter().
Another method would be to add callbacks which you connect once you initialize the GridView in your DetailViewController. A callback is essentially a closure:
var callback : (() -> Void)?
which you can instantiate when needed, e.g.
// In DetailViewController initialization
gridView = GridView()
gridView.callback = { self.doSomething() }
In GridView you can trigger the callback like this:
func onButton()
{
callback?()
}
The callback will only execute, if unwrapping succeeds. Please ensure, that you have read Automatic Reference Counting, because these constructs may lead to strong reference cycles.
What's the difference? You can connect the callback only once (at least with the method I've showed here), but when it triggers, the receiver immediately executes its code. For notifications, you can have multiple receivers but there is some delay in event delivery.
Lets assume your GridView implementation is like as follows:
class GridView : UIView {
// Initializing buttons
let button1:UIButton = UIButton(...)
let button2:UIButton = UIButton(...)
// ...
// Adding buttons to view
self.addSubview(button1)
self.addSubview(button2)
// ...
}
Now, we will add selector methods which will be called when a button is touched. Lets assume implementation of your view controller is like as follows:
class DetailViewController : UIViewController {
let myView:GridView = GridView(...)
myView.button1.addTarget(self, action: "actionForButton1:", forControlEvents: UIControlEvents.TouchUpInside)
myView.button2.addTarget(self, action: "actionForButton2:", forControlEvents: UIControlEvents.TouchUpInside)
// ...
func actionForButton1(sender: UIButton!) {
// Your actions when button 1 is pressed
}
// ... Selectors for other buttons
}
I have to say that my example approach is not a good example for encapsulation principles of Object-Oriented Programming, but I have written like this because you are new to Swift and this code is easy to understand. If you want to prevent duplicate codes such as writing different selectors for each button and if you want to set properties of your view as private to prevent access from "outside" like I just did in DetailViewController, there are much much better solutions. I hope it just helps you!
I think you better create a class called GridView that is inherited from the UIView. Then, you can connect all you UI element with you class as IBOutlet or whatever using tag something like that. Later on, you can ask the instance of GridView in DetailViewController so that you can connect as IBAction.
Encapsulation is one of the principles of OOP.