How do I use an enum within a kotlin data class

Question

I have this model

data class HourlyModel(
    val time: String,
    @DrawableRes val image: Int,
    val temp: Double
)

I realized that the server will provide me with weather codes which translate to the icon that will be displayed. I think if I pull the @DrawableRes into an enum, it maybe better because I have a model for Today's Weather and WeeklyWeather forecasts.

All 3 models will be using the same weather codes. I am new to Kotlin but I think if I have an enum class, I should be able to somehow use this within each model

enum class WeatherTypes (
    val weatherCode: Int,
    @DrawableRes val drawable: Int
) {
    SUNNY(0, R.drawable.sunny_t),
    RAIN(1,R.drawable.rain_t);
    
    companion object {
        fun weatherToImage(weatherCode: Int) = when(weatherCode) {
            0 -> SUNNY
            1 -> RAIN
            else -> SUNNY
        }
    }
}

Can someone help me out and tell me what I should do to my model to use this enum class to replace the @DrawableRes? if I can't then what is the best option for me?

Xid · Accepted Answer · 2020-10-25 10:26:44Z

3

I'll assume you have different models for different layers. Let's say you have a data class for the data you receive from the server.

data class HourlyDto(
    val time: String,
    val weatherCode: Int,
    val temp: Double,
)

Your domain model will be something like so:

data class HourlyModel(
    val time: String,
    val weatherType: WeatherType,
    val temp: Double,
)

I've refactored your enum class:

enum class WeatherType(
    @DrawableRes val imageResId: Int,
) {
    SUNNY(R.drawable.sunny_t),
    RAIN(R.drawable.rain_t);

    companion object {
        fun from(weatherCode: Int): WeatherType {
            return WeatherType.values()[weatherCode]
        }
    }
}

Now, you can map your remote model to your domain model. Let's create an extension function for doing that( for the sake of example. You may be doing it another way )

fun HourlyDto.mapToModel(): HourlyModel {
    return HourlyModel(
        time,
        WeatherType.from(weatherCode),
        temp
    )
}

Finally, you can use you can get your drawable resource-id like so:

val hourlyWeather: HourlyModel = ...
hourlyWeather.weatherType.imageResId

Note: This answers the question of how to use the enum in your model class, but I guess to solve this specific issue you could use original model(with drawable resource-id) and then create a helper function that takes in weathercode and returns the drawable resource-id and reuse that wherever required.

answered Oct 25, 2020 at 10:26

Xid

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3 Comments

GettingStarted Over a year ago

Why did you remove the val weatherCode: Int, from WeatherTypes?

Xid Over a year ago

I removed it because it is the same as the oridinal for the enum. The code you have provided does not show any concrete use of weatherCode, you don't have it in your original model (the first one). It's up to you, depending on your app's functionality you may want to put it in the enum class.

SMBiggs Over a year ago

Damn that's awkward. Definitely not worth the trouble, sigh.

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