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/*
* Copyright 2018 Allan Wang
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ca.allanwang.kau.kotlin
/**
* Created by Allan Wang on 26/12/17.
*
* Kotlin implementation of a flyweight design pattern
* Values inside the map will be returned directly
* Otherwise, it will be created with the supplier, saved, and returned
* In the event a default is provided, the default takes precedence
*/
fun <K : Any, V : Any> flyweight(creator: (K) -> V) = FlyWeight(creator)
class FlyWeight<K : Any, V : Any>(private val creator: (key: K) -> V) : Map<K, V> {
private val map = mutableMapOf<K, V>()
override val entries: Set<Map.Entry<K, V>>
get() = map.entries
override val keys: Set<K>
get() = map.keys
override val size: Int
get() = map.size
override val values: Collection<V>
get() = map.values
override fun containsKey(key: K) = map.containsKey(key)
override fun containsValue(value: V) = map.containsValue(value)
override fun getOrDefault(key: K, defaultValue: V) = map.getOrDefault(key, defaultValue)
override fun isEmpty() = map.isEmpty()
override fun get(key: K): V {
if (!map.containsKey(key))
map.put(key, creator(key))
return map[key]!!
}
}
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