Using isKindOfClass with Swift
I'm trying to pick up a bit of Swift lang and I'm wondering how to convert the following Objective-C into Swift:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[super touchesBegan:touches withEvent:event];
UITouch *touch = [touches anyObject];
if ([touch.view isKindOfClass: UIPickerView.class]) {
//your touch was in a uipickerview ... do whatever you have to do
}
}
More specifically I need to know how to use isKindOfClass
in the new syntax.
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
???
if ??? {
// your touch was in a uipickerview ...
}
}
The proper Swift operator is is
:
if touch.view is UIPickerView {
// touch.view is of type UIPickerView
}
Of course, if you also need to assign the view to a new constant, then the if let ... as? ...
syntax is your boy, as Kevin mentioned. But if you don't need the value and only need to check the type, then you should use the is
operator.
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
super.touchesBegan(touches, withEvent: event)
let touch : UITouch = touches.anyObject() as UITouch
if touch.view.isKindOfClass(UIPickerView)
{
}
}
Edit
As pointed out in @Kevin's answer, the correct way would be to use optional type cast operator as?
. You can read more about it on the section Optional Chaining
sub section Downcasting
.
Edit 2
As pointed on the other answer by user @KPM, using the is
operator is the right way to do it.
You can combine the check and cast into one statement:
let touch = object.anyObject() as UITouch
if let picker = touch.view as? UIPickerView {
...
}
Then you can use picker
within the if
block.
I would use:
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
super.touchesBegan(touches, withEvent: event)
let touch : UITouch = touches.anyObject() as UITouch
if let touchView = touch.view as? UIPickerView
{
}
}