When I try to observe the progress of a NSBundleResourceRequest, observeValue(forKeyPath: object: change: context:) is not called for the .new observing option. Here is the setup and code:
Setup:
Xcode 8.3.1
Deployment Target iOS 10.3
Device: iPad 4
Resource tags (368 KB) are located located in Download Only On Demand and consist of thumbnails displayed in a UICollectionView.
Images are correctly displayed in the collection view.
Code:
final class MyCollectionVC: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
var myCollectionVCResourceRequest: NSBundleResourceRequest!
var myCollectionVCResourceRequestLoaded = false
static var myCollectionProgressObservingContext = UUID().uuidString
private let designThumbnailTags: Set<String> = ["Tag1", "Tag2", "Tag3"]
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
loadOnDemandResources()
}
func loadOnDemandResources() {
myCollectionVCResourceRequest = NSBundleResourceRequest(tags: designThumbnailTags)
myCollectionVCResourceRequest.progress.addObserver(self, forKeyPath: "fractionCompleted", options: [.new, .initial], context: &MyCollectionVC.myCollectionProgressObservingContext)
myCollectionVCResourceRequest.beginAccessingResources(completionHandler: { (error) in
print("Complete: \(self.myCollectionVCResourceRequest.progress.fractionCompleted)") // Prints Complete: 0.0
self.myCollectionVCResourceRequest.progress.removeObserver(self, forKeyPath: "fractionCompleted", context: &MyCollectionVC.myCollectionProgressObservingContext)
OperationQueue.main.addOperation({
guard error == nil else { self.handleOnDemandResourceError(error! as NSError); return }
self.myCollectionVCResourceRequestLoaded = true
self.updateViewsForOnDemandResourceAvailability()
self.fetchDesignThumbnailsWithOnDemandResourceTags(self.myCollectionVCResourceRequest) // Correctly creates Core Data Instances
})
})
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if context == &MyCollectionVC.myCollectionProgressObservingContext {
OperationQueue.main.addOperation({
let progressObject = object as! Progress
self.progressView.progress = Float(progressObject.fractionCompleted)
print(Float(progressObject.fractionCompleted)) // Prints 0.0 as a result of including the .initial option
self.progressDetailLabel.text = progressObject.localizedDescription
})
}
else {
super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
}
}
}
