PreferenceDelegates.kt

import android.content.SharedPreferences
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

fun SharedPreferences.boolProperty(key: String, defaultValue: Boolean)
        = preferenceProperty(this, { getBoolean(key, defaultValue) }, { putBoolean(key, it) })

fun SharedPreferences.floatProperty(key: String, defaultValue: Float)
        = preferenceProperty(this, { getFloat(key, defaultValue) }, { putFloat(key, it) })

fun SharedPreferences.intProperty(key: String, defaultValue: Int)
        = preferenceProperty(this, { getInt(key, defaultValue) }, { putInt(key, it) })

fun SharedPreferences.longProperty(key: String, defaultValue: Long)
        = preferenceProperty(this, { getLong(key, defaultValue) }, { putLong(key, it) })

fun SharedPreferences.stringProperty(key: String, defaultValue: String)
        = preferenceProperty(this, { getString(key, defaultValue) }, { putString(key, it) })

fun SharedPreferences.stringSetProperty(key: String, defaultValues: Set<String>)
        = preferenceProperty(this, { getStringSet(key, defaultValues) }, { putStringSet(key, it) })


private inline fun <T> preferenceProperty(
        sharedPreferences: SharedPreferences,
        crossinline getter: SharedPreferences.() -> T,
        crossinline setter: SharedPreferences.Editor.(T) -> SharedPreferences.Editor
): ReadWriteProperty<Any?, T> {
    return object : ReadWriteProperty<Any?, T> {
        override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
            sharedPreferences.edit().setter(value).apply()
        }

        override fun getValue(thisRef: Any?, property: KProperty<*>): T {
            return sharedPreferences.getter()
        }
    }
}