Implements circular/ring collection with expiring (based on an item insertion timestamp) elements. It was originally created to extract the Google Native Ads expiration logic from the main codebase. I considered adding a Sequence/IteratorProcol conformance, but decided not to do it as default/non-looping iterator would need to keep track of collection updates to be able to stop from going over collection multiple/infinite times. Besides, it would make the implementaion more complex which is not needed (yet).
I tried to cover all possible edge cases with tests, please let me know if I should add any.
This library was created to store some(small) number of elements those need to expire after some time. Collection (ExpiringStorage<T>) instance is intended to be shared across multiple places so implementation is based on class rather than a struct. Collection removes expired elements on addNew() automatically (clearExpired), while keeping track on the last provided element (by nextValid) to support continious/circular "read" behavior.
Expiration is controlled by the expirationInterval in the collection constructor (.init(expirationInterval: TimeInterval)), once the time since item insertion timestamp exceeds this interval - item considered expired and is not returned by nextValid/allValid and going to be removed from the collection on clearExpired (or addNew()).
import ExpiringStorage
...
private lazy var storage = ExpiringStorage<Object>(expirationInterval: 3600.0) //1 hour
private let requiredNumberOfElements = 5
...
override func viewWillAppear(_ animated: Bool) { {
super.viewWillAppear(animated)
loadIfNeeded()
...
}
...
private func loadIfNeeded() {
if storage.numberOfValidElements < requiredNumberOfElements {
loadMore()
}
}
private func loadMore() {
network.getObject { object in
storage.addNew(object)
updateUI()
loadIfNeeded()
}
}
private func showObject(in parentView: UIView) {
guard let object = storage.nextValid else {
showObjectPlaceholder()
return
}
...
}Add it to the dependencies value of your Package.swift:
dependencies: [
// ...
.package(url: "https://github.com/bivant/ExpiringStorage.git"),
],ExpiringStorage is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod 'ExpiringStorage'bivant, [email protected]
ExpiringStorage is available under the MIT license. See the LICENSE file for more info.