Design-Patterns

In the previous tutorial, you learned about inline functions and reified types. Now let’s learn about DSLs. A DSL (Domain-Specific Language) is a small language designed for a specific task. Kotlin makes it easy to create DSLs using lambdas with receivers. In this tutorial, you will learn: Lambdas with receiver Building a config DSL Nested DSL builders @DslMarker annotation HTML builder DSL Route DSL Query builder DSL Gradle-style DSL What is a DSL? A DSL is a language designed for a specific domain. You already use Kotlin DSLs every day: ...

In the previous tutorial, you learned about error handling. Now let’s learn about delegation. Delegation is a design pattern where an object hands off work to another object. Kotlin has built-in support for delegation using the by keyword. In this tutorial, you will learn: by lazy — lazy initialization Delegates.observable — react to changes Delegates.vetoable — reject invalid changes Map delegation — properties from a map Custom delegates — build your own Class delegation — delegate interface implementation by lazy by lazy creates a property that is computed only once, the first time you access it. After that, the cached value is returned. This is useful for expensive initialization. ...