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+--- Thread: Animate MapKit annotation coordinate change in Swift? (/Thread-Animate-MapKit-annotation-coordinate-change-in-Swift)
Animate MapKit annotation coordinate change in Swift? - marieuzmridi - 07-19-2023
When using MapKit in iOS 8 in Swift, how do I make it possible to animate a change in the map position of a custom annotation? I am saying this:
UIView.animateWithDuration(0.25) {
var loc = ann.coordinate
loc.latitude = loc.latitude + 0.0005
loc.longitude = loc.longitude + 0.001
ann.coordinate = loc
}
...where `ann` is a custom annotation, MyAnnotation. The annotation is jumping, not animating, to the new coordinate position.
**The annoying thing is that the animation works perfectly _if I write MyAnnotation in Objective-C_. But if I write it in Swift, I don't get the animation any more!**
Just FYI, here is my Swift code for MyAnnotation:
class MyAnnotation : NSObject, MKAnnotation {
var coordinate : CLLocationCoordinate2D
var title: String!
var subtitle: String!
init(location coord:CLLocationCoordinate2D) {
self.coordinate = coord
super.init()
}
}
RE: Animate MapKit annotation coordinate change in Swift? - amary742 - 07-19-2023
You almost have it right! Just change this line in your MyAnnotation implementation:
var coordinate : CLLocationCoordinate2D
to this:
dynamic var coordinate : CLLocationCoordinate2D
That will fix it.
Why does this matter? Because annotation animation relies on KVO (key value observing). In Swift, a property is not key value observable unless it is marked as `dynamic`. (To get a little more technical, that in turn is because KVO observation works by swizzling the implementation of the property setter method - the runtime reaches right into your class and changes that property's setter code. But in Swift, it can't do that unless you explicitly mark the property as `dynamic`.)