Learning Center

Kotlin Engine

This engine generates models in Kotlin code. It relies on the following kotlinx libraries:

kotlinx.serialization: for JSON serialization
kotlinx.datetime: for date/datetime data types

Getting Started

Once you add a Kotlin engine, you should navigate to the engine config and set a package for the Kotlin models, just like we did in the screenshot below. Of course your package probably won't be io.onegen.models.

Gradle Config

Let's take a look at what needs to be configured to get the Kotlin models working in your project.

Add dependencies

As mentioned above, Kotlin engine relies on a few dependencies. Add them to your gradle's dependencies block.

  dependencies {
    // other dependencies in your project

    implementation 'org.jetbrains.kotlinx:kotlinx-datetime:0.4.0'
    implementation 'org.jetbrains.kotlinx:kotlinx-serialization-json:1.4.0'
}

Add the serialization plugin

Add the following line to your plugins block.

  plugins {
    // other plugins in your project

    id 'org.jetbrains.kotlin.plugin.serialization' version '1.6.10'
}

Then apply the plugin by adding:

apply plugin: 'kotlinx-serialization'

Important: Make sure to update the versions kotlinx-datetime and kotlinx-serialization versions.

Hello Kotlin Example

We published an example repository where we generated Kotlin models of a simple Notes app. You can see the necessary gradle setup as well as some model code.

Data Types

Standard

Since java doesn't support unsigned data types, all unsigned data types are expressed as signed data types.

Design	Kotlin
bool	Boolean
int	Int
int8	Byte
int16	Short
int32	Int
int64	Long
uint	UInt
uint8	UByte
uint16	UShort
uint32	UInt
uint64	ULong
float	Float
double	Double
string	String
char	Char
byte	Byte
bytea	ByteArray
date	LocalDate
datetime	LocalDateTime

Complex

Name	Kotlin Type
Array	List
Map	Map

Why is Android Room not supported?

We'd love to support the Room database, but its relationship implementation is quite restrictive. We ultimately decided it was out of our scope, we found a way to support you though.

If your project uses the Room database, there are two ways to integrate OneGen models:

a) Using the @Embedded feature

Create wrapper models and use the @Embedded feature to embed the OneGen models.

b) Using Inheritance

Go to the Kotlin config and in Kotlin's General section, do the following:

In Class Type select box, pick Regular
Check the Open Class switch
Now implement your Room models by inheriting from OneGen models