DelegatedPreference

DelegatedPreference.kt

public class DelegatedPreference<T>(val default: T, val preferencesManagerInstantiator:()->SharedPreferences) {

    val manager : SharedPreferences by Delegates.lazy(preferencesManagerInstantiator)

    [suppress("UNCHECKED_CAST")]
    fun get(thisRef: Any?, prop: PropertyMetadata): T {
       return when(default){
            is Int -> manager.getInt(prop.name, this.default) as T
            else -> throw TypeNotImplementedException(prop.name)
        }
    }

    fun set(thisRef: Any?, prop: PropertyMetadata, value: T) {
        when(value){
            is Int -> manager.edit().putInt(prop.name, value ).apply()
            else -> throw TypeNotImplementedException(prop.name)
        }
    }
    
    class TypeNotImplementedException(val propName:String) : Exception("Type of ${propName} is not implemented on DelegatedPreference and thus invalid")
}