SharedPreferences under Delegated properties - PreferencesDelegate without implementation.

PreferencesDelegate.kt

open class PreferencesDelegate<T>(private val key: String) {
    private var variable: Any? = null

    /**
     * Performing operation on synchronized thread.
     * @param thisRef - is the reference to the class that contains the property
     * @param property - is an instance of the [KProperty] class, which contains metadata.
     * @return T - desired value by a given key or null.
     */
    open operator fun getValue(thisRef: Any?, property: KProperty<*>): T? {
        //...nothing for now
    }

    /**
     * Saves given value to SharedPreferences on synchronized thread.
     * @param thisRef - is the reference to the class that contains the property
     * @param property - is an instance of the [KProperty] class, which contains metadata.
     */
    open operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
       //...nothing for now
    }
    
    /**
     * Add [resetCache] into specific [cacheCleaners].
     * @return - PreferencesDelegate<T>.
     */
    fun addCacheCleaners(cacheCleaners: MutableList<(() -> Unit)>) = apply {
        cacheCleaners.add { this.resetCache() }
    }

    /**
     * Clear cached value.
     */
    private fun resetCache() {
        variable = null
    }
}