Fragment Navigation Pattern

DataSource.kt

interface DataSourceBase

class DataSource {
    companion object {
        private var sInstance: DataSource? = null
        private var LOCK = Any()

        fun getInstance(): DataSource? {
            synchronized(LOCK) {
                if (sInstance == null) {
                    sInstance = DataSource()
                }
            }
            return sInstance
        }
    }

    private var map: WeakHashMap<Any, DataSourceBase> = WeakHashMap()

    fun <R : DataSourceBase> push(key: Any, data: R?) {
        data?.let {
            map.put(key, data)
        }
    }

    @Suppress("UNCHECKED_CAST")
    fun <R : DataSourceBase> peek(key: Any): R? {
        return map[key] as? R?
    }

    @Suppress("UNCHECKED_CAST")
    fun <R : DataSourceBase> pop(key: Any): R? {
        val data = map[key] as R
        map.remove(key)
        return data
    }

    fun remove(key: Any) {
        map.remove(key)
    }
}