On-demand resources

onboarding.swift

private lazy var bundleResourceRequest = NSBundleResourceRequest(tags: Set(["Onboarding"]))

private func loadOnDemandAssets() {
    bundleResourceRequest.conditionallyBeginAccessingResources { [unowned self] (available) in
        if available {
            self.loadOnboardingAssets()
        } else {
            self.bundleResourceRequest.beginAccessingResources { (error) in
                guard error == nil else { return }
                self.loadOnboardingAssets()
            }
        }
    }
}

private func discardOnDemandAssets() {
    bundleResourceRequest.endAccessingResources()
}