HI, all. I'm looking for a recommendation for a KMP library to cache images from the web and cache t...

# multiplatform

[Darryl Pierce]

HI, all. I'm looking for a recommendation for a KMP library to cache images from the web and cache them locally. Not looking for a UI widget, but for a library that, when given a URL, could load the image, cache it on the device, and retrieve it from the cache as needed. Anybody have a preferred library? I looked at and rejected COIL since it seems to want to be a UI piece, something I don't need or want.

[streetsofboston]

What about Ktor Client, with http caching enabled?
https://api.ktor.io/ktor-client/ktor-client-core/io.ktor.client.plugins.cache/-http-cache/index.html
https://api.ktor.io/ktor-client/ktor-client-core/io.ktor.client.plugins.cache.storage/-file-storage.html

[Darryl Pierce]

Does it do persistent caching? I wasn't aware of that feature.

[streetsofboston]

You can combine those two to create persistent storage.

This is what Gemini came up with

import io.ktor.client.*
import io.ktor.client.engine.cio.*
import io.ktor.client.plugins.cache.*
import io.ktor.client.plugins.cache.storage.*
import java.io.File

fun main() {
    val cacheDirectory = File("my_app_cache")
    val client = HttpClient(CIO) {
        install(HttpCache) {
            publicStorage(FileStorage(cacheDirectory)) // Use FileStorage for persistent caching
        }
    }

// ... make HTTP requests with the client ...
}

[Darryl Pierce]

Excellent! Thank you for that. 😄

[Darryl Pierce]

@streetsofboston QQ - the above code works across both iOS and Android? I'm expecting I can put the above inside of my viewmodel as part of the initialization of the app state, yeah?

[streetsofboston]

Ah... "FileStorage" only works for JVM....

[streetsofboston]

You could use dependency inversion and injection, or expect/actual construct to user FileStorage for Android and use URLSessionConfiguration on iOS.

[Darryl Pierce]

kk - will give that a try.

[streetsofboston]

Maybe this will help:
Use KtorNSURLSessionDelegate in iosMain module.
Not sure if this works directly, but maybe this helps?

import io.ktor.client.engine.darwin.Darwin
import io.ktor.client.engine.darwin.DarwinClientEngineConfig
import io.ktor.client.engine.darwin.KtorNSURLSessionDelegate
import io.ktor.client.HttpClient
import platform.Foundation.NSURLCache
import platform.Foundation.NSURLRequestReloadIgnoringLocalCacheData
import platform.Foundation.NSURLSession
import platform.Foundation.NSURLSessionConfiguration

val client = HttpClient(Darwin) {
    engine {
        val ktorDelegate = KtorNSURLSessionDelegate()
        val sessionConfiguration = NSURLSessionConfiguration.defaultSessionConfiguration().apply {
            urlCache = NSURLCache.sharedURLCache()
            requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData
        }
        val session = NSURLSession.sessionWithConfiguration(
            configuration = sessionConfiguration,
            delegate = ktorDelegate,
            delegateQueue = null
        )

        // Pass the preconfigured session and delegate to the Ktor engine.
        usePreconfiguredSession(session, ktorDelegate)
    }
}

[Darryl Pierce]

@streetsofboston That definitely looks more promising.

[Albilaga]

https://github.com/vipulasri/kachetor I am using this to persist both android and iOS. You can take a look on there how it works. it is basically the same as using expect and actual