Unlocking the Power of Sealed Classes in Kotlin

What are Sealed Classes?

Sealed classes represent a restricted class hierarchy, enabling you to define subclasses within the scope of the parent function, allowing you to represent hierarchies. In other words, sealed classes limit the types of objects that can be created, making your code more predictable and comprehensive.

Sealed Classes vs. Enum Classes

Enum classes are used to store a list of constants representing a set of types of a single object. However, enum classes have limitations. They can only have a single instance of each value, and each enum constant exists only as a single instance. Sealed classes, on the other hand, offer more flexibility. They can have multiple instances of each subclass, and each subclass can have its own properties and behavior.

Using Sealed Classes with the When Expression

Kotlin’s when expression is a powerful tool for handling different possibilities. When used with sealed classes, the when expression can exhaustively cover all possible cases, ensuring that your code is robust and error-free.

Managing States in Kotlin

Sealed classes are particularly useful for managing states in Kotlin. By defining a sealed class with different subclasses, you can represent different states, such as loading, success, and error. This approach allows you to write more comprehensive and predictable code, making it easier to handle different scenarios.

Real-World Example: Data Loading States

Let’s consider a real-world example of using sealed classes to manage data loading states. We can define a sealed class with three subclasses: Loading, Success, and Error. Each subclass can have its own properties and behavior, allowing us to handle different scenarios.

sealed class DataLoadingState {
    object Loading : DataLoadingState()
    data class Success(val data: List<String>) : DataLoadingState()
    data class Error(val message: String) : DataLoadingState()
}

By using sealed classes, we can ensure that our code is robust and error-free. The when expression can exhaustively cover all possible cases, making it easier to handle different scenarios.

For example, we can use the when expression to handle different data loading states:

fun handleDataLoadingState(state: DataLoadingState) {
    when (state) {
        is DataLoadingState.Loading -> println("Loading...")
        is DataLoadingState.Success -> println("Data loaded successfully: ${state.data}")
        is DataLoadingState.Error -> println("Error loading data: ${state.message}")
    }
}

This approach ensures that we have covered all possible cases, making our code more robust and error-free.