Create kpref single

1 files changed, 53 insertions, 0 deletions

diff --git a/core/src/main/kotlin/ca/allanwang/kau/kpref/KPrefSingleDelegate.kt b/core/src/main/kotlin/ca/allanwang/kau/kpref/KPrefSingleDelegate.kt
new file mode 100644
index 0000000..58e570f
--- /dev/null
+++ b/core/src/main/kotlin/ca/allanwang/kau/kpref/KPrefSingleDelegate.kt
@@ -0,0 +1,53 @@
+package ca.allanwang.kau.kpref
+
+import ca.allanwang.kau.kotlin.ILazyResettable
+
+/**
+ * Created by Allan Wang on 2017-06-07.
+ */
+fun KPref.kprefSingle(key: String) = KPrefSingleDelegate(key, this)
+
+/**
+ * Singular KPref Delegate for booleans
+ * When the shared pref is not initialized, it will return true then set the pref to false
+ * All subsequent retrievals will be false
+ * This is useful for one time toggles such as showcasing items
+ */
+class KPrefSingleDelegate internal constructor(private val key: String, private val pref: KPref, lock: Any? = null) : ILazyResettable<Boolean> {
+
+    @Volatile private var _value: Boolean? = null
+    private val lock = lock ?: this
+
+    init {
+        if (pref.prefMap.containsKey(key))
+            throw KPrefException("$key is already used elsewhere in preference ${pref.PREFERENCE_NAME}")
+        pref.prefMap.put(key, this@KPrefSingleDelegate)
+    }
+
+    override fun invalidate() {
+        _value = null
+    }
+
+    override val value: Boolean
+        get() {
+            val _v1 = _value
+            if (_v1 != null)
+                return _v1
+
+            return synchronized(lock) {
+                val _v2 = _value
+                if (_v2 != null) {
+                    _v2
+                } else {
+                    _value = pref.sp.getBoolean(key, true)
+                    if (_value!!) pref.sp.edit().putBoolean(key, false).apply()
+                    _value!!
+                }
+            }
+        }
+
+    override fun isInitialized(): Boolean = _value != null
+
+    override fun toString(): String = if (isInitialized()) value.toString() else "Lazy kPref $key not initialized yet."
+
+}
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