1 files changed, 51 insertions, 0 deletions
diff --git a/app/src/main/kotlin/com/pitchedapps/frost/utils/LazyResettable.kt b/app/src/main/kotlin/com/pitchedapps/frost/utils/LazyResettable.kt
new file mode 100644
index 00000000..c8365f5c
--- /dev/null
+++ b/app/src/main/kotlin/com/pitchedapps/frost/utils/LazyResettable.kt
@@ -0,0 +1,51 @@
+package com.pitchedapps.frost.utils
+
+import java.io.Serializable
+import kotlin.reflect.KProperty
+
+/**
+ * Created by Allan Wang on 2017-05-30.
+ *
+ * Lazy delegate that can be invalidated if needed
+ * https://stackoverflow.com/a/37294840/4407321
+ */
+private object UNINITIALIZED
+
+fun <T : Any> lazyResettable(initializer: () -> T): LazyResettable<T> = LazyResettable<T>(initializer)
+
+class LazyResettable<T : Any>(private val initializer: () -> T, lock: Any? = null) : Lazy<T>, Serializable {
+    @Volatile private var _value: Any = UNINITIALIZED
+    private val lock = lock ?: this
+
+    fun invalidate() {
+        _value = UNINITIALIZED
+    }
+
+    override val value: T
+        get() {
+            val _v1 = _value
+            if (_v1 !== UNINITIALIZED)
+                @Suppress("UNCHECKED_CAST")
+                return _v1 as T
+
+            return synchronized(lock) {
+                val _v2 = _value
+                if (_v2 !== UNINITIALIZED) {
+                    @Suppress("UNCHECKED_CAST")
+                    _v2 as T
+                } else {
+                    val typedValue = initializer()
+                    _value = typedValue
+                    typedValue
+                }
+            }
+        }
+
+    override fun isInitialized(): Boolean = _value !== UNINITIALIZED
+
+    override fun toString(): String = if (isInitialized()) value.toString() else "Lazy value not initialized yet."
+
+    operator fun setValue(any: Any, property: KProperty<*>, t: T) {
+        _value = t
+    }
+}
+\ No newline at end of file