Create flyweight (#118)

1 files changed, 40 insertions, 0 deletions

diff --git a/core/src/main/kotlin/ca/allanwang/kau/kotlin/FlyWeight.kt b/core/src/main/kotlin/ca/allanwang/kau/kotlin/FlyWeight.kt
new file mode 100644
index 0000000..03e98d2
--- /dev/null
+++ b/core/src/main/kotlin/ca/allanwang/kau/kotlin/FlyWeight.kt
@@ -0,0 +1,40 @@
+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]!!
+    }
+
+}
\ No newline at end of file