How to Efficiently Map Kotlin Data Classes to Similar Data Classes

What is the best way to map similar Kotlin data classes for tasks such as converting form data to database records?

data class PersonForm(
    val firstName: String,
    val lastName: String,
    val age: Int,
    val tel: String
)

data class PersonRecord(
    val name: String, // "${firstName} ${lastName}"
    val age: Int,
    val tel: String
)

Mapping Kotlin data classes can streamline your application's data transformation processes, especially when dealing with layers such as database entities and form models. Unlike Java, Kotlin provides unique features that make this task more straightforward while avoiding common pitfalls associated with conventional mapping techniques.

fun mapPersonFormToRecord(form: PersonForm): PersonRecord {
    return PersonRecord(
        name = "${form.firstName} ${form.lastName}",
        age = form.age,
        tel = form.tel
    )
}

Causes

• The need to convert data objects between different layers of an application, such as from a database entity to a form model or an API response.
• Kotlin's data classes are final and cannot be modified using traditional reflection-based libraries like ModelMapper.
• Maintaining data accuracy between differently-structured classes that share similar attributes.

Solutions

• Utilize Kotlin's copy function to create a new instance while modifying properties as needed.
• Implement extension functions which allow mapping through more concise and readable code.
• Leverage libraries such as MapStruct or Kotlin's built-in functions for mapping.
• Consider using third-party libraries like KMapper, DoMapper, or WriteMapper tailored for Kotlin for hassle-free mapping.

Mistake: Overly complex mapping functions that do not leverage Kotlin's features.

Solution: Simplify mappings by using Kotlin's extension functions and enhancing readability.

Mistake: Neglecting default parameter values which can lead to unintended results in mappings.

Solution: Always ensure parameters are properly accounted for in your mapping functions.