Kotlin Delegated properties Delegate Can be used as a layer to reduce boilerplate
Example
Consider Kotlin's Null Type system and WeakReference<T>.
So let's say we have to save some sort of reference and we wanted to avoid memory leaks, here is where WeakReference comes in.
take for example this:
class MyMemoryExpensiveClass {
companion object {
var reference: WeakReference<MyMemoryExpensiveClass>? = null
fun doWithReference(block: (MyMemoryExpensiveClass) -> Unit) {
reference?.let {
it.get()?.let(block)
}
}
}
init {
reference = WeakReference(this)
}
}
Now this is just with one WeakReference. To Reduce this boilerplate, we can use a custom property delegate to help us like so:
class WeakReferenceDelegate<T>(initialValue: T? = null) : ReadWriteProperty<Any, T?> {
var reference = WeakReference(initialValue)
private set
override fun getValue(thisRef: Any, property: KProperty<*>): T? = reference.get()
override fun setValue(thisRef: Any, property: KProperty<*>, value: T?) {
reference = WeakReference(value)
}
}
So Now we can use variables that are wrapped with WeakReference just like normal nullable variables !
class MyMemoryExpensiveClass {
companion object {
var reference: MyMemoryExpensiveClass? by WeakReferenceDelegate<MyMemoryExpensiveClass>()
fun doWithReference(block: (MyMemoryExpensiveClass) -> Unit) {
reference?.let(block)
}
}
init {
reference = this
}
}
