ApiResult

ApiResult is a Kotlin Multiplatform declarative error handling framework that is performant, easy to use and feature-rich.

ApiResult is Railway Programming and functional error handling on steroids.

Features

• ApiResult is lightweight. The library creates no objects, makes no allocations or virtual function resolutions. Most of the code is inlined.
• ApiResult offers 90+ operators covering most of possible use cases to turn your code from imperative and procedural to declarative and functional, which is more readable and extensible.
• ApiResult defines a contract that you can use in your code. No one will be able to obtain the result of a computation without being forced to handle errors at compilation time.
• The library has 129 tests for 92% operator coverage.

Preview

// wrap a result of a computation and expose the result
class BillingRepository(private val api: RestApi) {

    suspend fun getSubscriptions() = ApiResult {
        api.getSubscriptions()
    } // -> ApiResult<List<Subscription>?>
}

// ----- 

// obtain and handle the result in the client code
val repo = BillingRepository( /* ... */)

fun onClickVerify() {
    val state: SubscriptionState = repo.getSubscriptions()
        .errorOnNull() // map nulls to error states with compile-time safety
        .recover<NotSignedInException, _> { emptyList() } // recover from some or all errors
        .require { securityRepository.isDeviceTrusted() } // conditionally fail the chain
        .mapValues(::SubscriptionModel) // map list items
        .filter { it.isPurchased } // filter values
        .mapError<NetworkException, _, _> { e -> BillingException(cause = e) } // map exceptions
        .then { validateSubscriptions(it) } // execute a computation and continue with its result, propagating errors
        .chain { updateGracePeriod(it) } // execute another computation, and if it fails, stop the chain
        .onError { subscriptionService.disconnect() } // executed on error
        .onEmpty { return SubscriptionState.NotSubscribed } // use non-local returns and short-circuit evaluation
        .fold(
            onSuccess = { SubscriptionState.Subscribed(it) },
            onError = { SubscriptionState.Error(it) },
        ) // unwrap the result to another value
    // ...
}

Quickstart

• Documentation:
• KDoc:
• Latest version:

[versions]
apiresult = "< Badge above 👆🏻 >"

[dependencies]
apiresult = { module = "pro.respawn.apiresult:core", version.ref = "apiresult" } 

---

dependencies {
    // usually you will want to expose ApiResult types in your module APIs, so consider using api() for the dependency
    commonMainApi("pro.respawn.apiresult:core:<version>")
}

Ready to try? Start with reading the Quickstart Guide.

License

   Copyright 2022-2024 Respawn Team and contributors

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.