Example for Kotlin Generics - MyKotlinSharedPreference call when storing/retrieving any type of primitive data

KotlinGenerics.kt

//One very powerful example of Generics might in combination with delegates is creation of SharedPreferences support
//taken from Kotlin for Android Developers by Antonio Leiva

class MyKotlinSharedPreference<T>(val context: Context, val name: String, val default: T) {

  val prefs by lazy {
     context.getSharedPreferences("default", Context.MODE_PRIVATE)
 }

  //operator overloading
 operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
   return findPreference(name, default)
}

  //operator overloading
 operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
      putPreference(name, value)
 }
 
 //use when yo distingush type
 private fun <T> findPreference(name: String, default: T): T = with(prefs) {
        val res: Any = when (default) {
            is Long -> getLong(name, default)
            is String -> getString(name, default)
            is Int -> getInt(name, default)
            is Boolean -> getBoolean(name, default)
            is Float -> getFloat(name, default)
            else -> throw IllegalArgumentException("This type can't be saved into Preferences")
        }

        res as T
    }
  
  
 //use when yo distingush type
  private fun <U> putPreference(name: String, value: U) = with(prefs.edit()) {
        when (value) {
            is Long -> putLong(name, value)
            is String -> putString(name, value)
            is Int -> putInt(name, value)
            is Boolean -> putBoolean(name, value)
            is Float -> putFloat(name, value)
            else -> throw IllegalArgumentException("This type can be saved into Preferences")
        }.apply()
    }

}