Kotlin Delegate for persistant objects

GsonDelegatePref

package com.tobiasschuerg

import android.content.SharedPreferences
import com.google.gson.Gson
import com.google.gson.GsonBuilder
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

class GsonDelegatePref<T>(
    private val prefs: SharedPreferences,
    private val name: String,
    private val typeOfT: Class<T>,
    private val default: (() -> T?) = { null }
) : ReadWriteProperty<Any?, T?> {

    override fun getValue(thisRef: Any?, property: KProperty<*>): T? {
        val json: String? = prefs.getString(name, null)
        return if (json != null) {
            gson.fromJson(json, typeOfT)
        } else {
            default()
        }
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {
        val json: String? = value?.let { gson.toJson(value) }
        prefs.edit().putString(name, json).apply()
    }


    companion object {
        private val gson: Gson = GsonBuilder().setPrettyPrinting().create()
    }
}