Q & A
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observation = observe(
\.textView.contentSize,
options: [.new]
) {[unowned self] object, change in
}
Fatal error: Could not extract a String from KeyPath Swift.ReferenceWritableKeyPath<xxxx.xxxxxxTextViewDelegate, __C.CGSize>
Note the @objc keyword
References
https://developer.apple.com/documentation/swift/using-key-value-observing-in-swift
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class MyObserver: NSObject {
@objc var objectToObserve: MyObjectToObserve
var observation: NSKeyValueObservation?
init(object: MyObjectToObserve) {
objectToObserve = object
super.init()
observation = observe(
\.objectToObserve.myDate,
options: [.old, .new]
) { object, change in
print("myDate changed from: \(change.oldValue!), updated to: \(change.newValue!)")
}
}
}