iOS

All Apple calls live in the AssetDropKit Swift package. It picks Apple-hosted Background Assets on iOS 26 and later and On-Demand Resources on iOS 17 and 18. No Objective-C, and Kotlin never calls BackgroundAssets through cinterop.

1. Export the library from your Kotlin framework

iosTarget.binaries.framework {
    export("com.vocabloot:assetdropkit:0.1.1")
}

Swift then sees ApplePackStore, ApplePackCallbacks, PackCancel and PackFailure (.noNetwork, .insufficientStorage, ...).

2. Add the adapter

Copy templates/ios/AssetDropAdapter.swift into your app target and replace import Shared with your framework's module name. A Swift package cannot import your Kotlin framework, so this short file lives in the app.

3. Hand it to Kotlin

let store = AssetDropAdapter()                                   // App Store and TestFlight
let store = AssetDropAdapter(packs: AppleAssetPacks(onDemandResourcesOnly: true)) // Xcode runs on iOS 26

// iosMain
fun makePacks(store: ApplePackStore) = AssetPacks(source = AppleStoreSource(store = store))

AppleStoreSource resumes each call once (a late second callback is ignored), cancels the Swift task when your coroutine is cancelled, and copies file bytes out of NSData straight away.

4. Package the packs

See Packaging: the ODR folder reference and tag, the downloader extension, the App Group and the three Info.plist keys.

On-Demand Resources details

One NSBundleResourceRequest per fetched pack is held for the process's life at urgent loading priority, with the preservation priority raised so the system keeps the pack. remove ends access and lowers it; the system frees the space later.