Android Development with Kotlin

Providing a delegate

Since Kotlin 1.1, there is an operator, provideDelegate, that is used to provide a delegate during class initialization. The main motivation behind provideDelegate was that it allows us to provide a customized delegate depending on traits of property (name, type, annotations, and so on).

The provideDelegate operator returns a delegate, and types that have this operator do not need to be delegates themselves in order to be used as a delegate. Here is an example:

    class A(val i: Int) { 
 
        operator fun provideDelegate( 
            thisRef: Any?, 
            prop: KProperty<*> 
        ) = object: ReadOnlyProperty<Any?, Int> { 
 
            override fun getValue( 
                thisRef: Any?, 
                property: KProperty<*> 
            ) = i 
        } 
    } 
 
    val a by A(1) 

In this example, A is used as a delegate, while ...