Kotlin
Summary - Compiler plugins
Combine IR, all-open and no-arg to write a framework integration.
Summary - Compiler plugin
In this group you learned compiler plugin, IR, plugin vs KSP, all-open and no-arg. Now you will write a model that combines them: an open Entity and its subclass.
Your Entity will be open; its tag() method will also be open. A User subclass will override tag(). In main you will do a polymorphic assignment and print the result. This is a typical entity scenario where all-open and no-arg meet.
Combining: open Entity
Now we will do by hand what all-open does: mark Entity and tag() as open. Then add a subclass.
Example: open class Entity(val id: Int) { open fun tag(): String = "Entity" }. class User(id: Int) : Entity(id) { override fun tag(): String = "User" }. The assignment val e: Entity = User(7); the call e.tag() returns "User". This is polymorphic behaviour. The all-open plugin does this automatically; we model it. This structure is the basis of framework proxies.
Exercise Write Open Entity + User
Define open class Entity(val id: Int) with open fun tag(): String = "Entity". Define class User(id: Int) : Entity(id) with override fun tag(): String = "User". In main, write val e: Entity = User(7) and println("${'$'}{e.tag()}:${'$'}{e.id}").
Show example solution
open class Entity(val id: Int) {
open fun tag(): String = "Entity"
}
class User(id: Int) : Entity(id) {
override fun tag(): String = "User"
}
fun main() {
val e: Entity = User(7)
println("${e.tag()}:${e.id}")
}
Test yourself
-
Which action can only be done by a plugin?
- Read annotations
- Make a class open
- Return a list
- Generate a new file
Show answer
Make a class open — Making a class open modifies existing code; only a plugin can do it.
-
Complete the tag method
open class Entity(val id: Int) {
open fun ____(): String = "Entity"
}
Show answer
open class Entity(val id: Int) {
open fun tag(): String = "Entity"
}
-
Match plugin concepts
- all-open
- Makes a class open
- no-arg
- Adds a synthetic constructor
- IR
- Intermediate representation
- compose
- Transforms Composables
Next lesson: Kotlin/Native
