Add default value for the failure param in the result.fold

Description

result.fold should have a default value for failure parameter. Since return statement is not allowed in success and failure blocks now we need to define a nullable variable albums to store it.

    private suspend fun httpGetCoroutine(): List<AlbumNetworkModel> {
        var albums: List<AlbumNetworkModel>? = null
        
        Fuel.get("/albums").responseObject<List<AlbumNetworkModel>> { _, _, result ->
            result.fold(
                success = {
                    albums = it
                },
                failure = {
                    albums = listOf()
                })
        }
        
        return albums ?: listOf()
    }

Proposed Solution

However, with the default value for failure parameter, we could use the library in a more expressive way by assigning a default value to our albums variable

    private suspend fun httpGetCoroutine(): List<AlbumNetworkModel> {
        var albums: List<AlbumNetworkModel> = listOf()
        
        Fuel.get("/albums").responseObject<List<AlbumNetworkModel>> { _, _, result ->
            result.fold(
                success = {
                    albums = it
                })
        }
       
        return albums
    }

[SleeplessByte]

Responses should always have data or expect explicitly to not have data. “null” is a really bad indicator of no data and an empty list is much more expressive, but if you MUST you can use List<AlbumDomainModel>?. If you get an object with an non existing idea, you really should get back either an empty list or a 404 (which is an error).

I doubt getOrNull will be supported, because the whole point of Result is to NOT have to deal with null values.

On Thu, 8 Nov 2018 at 01:44 Igor Wojda [e-mail] wrote:

I had some time off… SogetOrElse did the trick for non-nullable types.

override suspend fun getAlbumList(): List<AlbumDomainModel> { val (_, _, result) = Fuel.get(“/albums”).awaitObjectResponse<List<AlbumNetworkModel>>(

gsonDeserializerOf())

    var albums = result.getOrElse(listOf())
    return albums.map { it.toDomainModel() }
}

However, I am still not sure how to simplify response that may not contain data (try to get object with non-existing id). getOrElse method does not allow to return null values, so either I am missing something or we need getOrNull method? 🤔

override suspend fun getAlbum(id: Int): AlbumDomainModel? {
    val (_, _, result) = Fuel.get("/albums/$id").awaitObjectResponse<AlbumNetworkModel>(gsonDeserializerOf())

    var album: AlbumNetworkModel? = null
    result.fold(success = { album = it }, failure = {})

    return album?.toDomainModel()
}

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[igorwojda]

I had some time off… SogetOrElse did the trick for non-nullable types.

override suspend fun getAlbumList(): List<AlbumDomainModel> {
        val (_, _, result) = Fuel.get("/albums").awaitObjectResponse<List<AlbumNetworkModel>>(gsonDeserializerOf())

        var albums = result.getOrElse(listOf())
        return albums.map { it.toDomainModel() }
    }

However, I am still not sure how to simplify response that may not contain data (try to get object with non-existing id). getOrElse method does not allow to return null values, so either I am missing something or we need new retult.getOrNull method ? 🤔

    override suspend fun getAlbum(id: Int): AlbumDomainModel? {
        val (_, _, result) = Fuel.get("/albums/$id").awaitObjectResponse<AlbumNetworkModel>(gsonDeserializerOf())

        var album: AlbumNetworkModel? = null
        result.fold(success = { album = it }, failure = {})

        return album?.toDomainModel()
    }