From 5dd926422529d129a74a56e528fb2516f76663c3 Mon Sep 17 00:00:00 2001
From: Yavor Georgiev <yavor.georgiev@outlook.com>
Date: Wed, 12 Jul 2017 13:02:21 +0200
Subject: [PATCH] Add `Realm.empty`

---
 CHANGELOG.md            |  2 +-
 docs/realm.js           |  8 ++++++++
 lib/browser/index.js    |  1 +
 lib/index.d.ts          |  1 +
 src/js_realm.hpp        |  9 +++++++++
 tests/js/realm-tests.js | 11 +++++++++++
 6 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e1d45805..f8cd8ae4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,7 @@ vNext Release notes (TBD)
 * None
 
 ### Enhancements
-* None
+* Added `Realm.prototype.empty` which is a property that indicates whether or not the realm has any objects in it.
 
 ### Bug fixes
 * Fix crash on Node.js when a listener callback throws an error.
diff --git a/docs/realm.js b/docs/realm.js
index 20fc99e3..0d7b5fca 100644
--- a/docs/realm.js
+++ b/docs/realm.js
@@ -23,6 +23,14 @@
  * ```
  */
 class Realm {
+   /**
+    * Indicates if this Realm contains any objects.
+    * @type {boolean}
+    * @readonly
+    * @since 1.10.0
+    */
+    get empty() {}
+
     /**
      * The path to the file where this Realm is stored.
      * @type {string}
diff --git a/lib/browser/index.js b/lib/browser/index.js
index e66ab2b9..81b2a804 100644
--- a/lib/browser/index.js
+++ b/lib/browser/index.js
@@ -52,6 +52,7 @@ function setupRealm(realm, realmId) {
     realm[keys.type] = objectTypes.REALM;
 
     [
+        'empty',
         'path',
         'readOnly',
         'schema',
diff --git a/lib/index.d.ts b/lib/index.d.ts
index 2fe62125..196b83d5 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -352,6 +352,7 @@ declare namespace Realm.Sync {
 declare class Realm {
     static defaultPath: string;
 
+    readonly empty: boolean;
     readonly path: string;
     readonly readOnly: boolean;
     readonly schema: Realm.ObjectSchema[];
diff --git a/src/js_realm.hpp b/src/js_realm.hpp
index 7614667d..2d9ac368 100644
--- a/src/js_realm.hpp
+++ b/src/js_realm.hpp
@@ -178,6 +178,7 @@ public:
     static void close(ContextType, FunctionType, ObjectType, size_t, const ValueType[], ReturnValue &);
 
     // properties
+    static void get_empty(ContextType, ObjectType, ReturnValue &);
     static void get_path(ContextType, ObjectType, ReturnValue &);
     static void get_schema_version(ContextType, ObjectType, ReturnValue &);
     static void get_schema(ContextType, ObjectType, ReturnValue &);
@@ -225,6 +226,7 @@ public:
     };
 
     PropertyMap<T> const properties = {
+        {"empty", {wrap<get_empty>, nullptr}},
         {"path", {wrap<get_path>, nullptr}},
         {"schemaVersion", {wrap<get_schema_version>, nullptr}},
         {"schema", {wrap<get_schema>, nullptr}},
@@ -501,6 +503,13 @@ void RealmClass<T>::set_default_path(ContextType ctx, ObjectType object, ValueTy
     js::set_default_path(Value::validated_to_string(ctx, value, "defaultPath"));
 }
 
+template<typename T>
+void RealmClass<T>::get_empty(ContextType ctx, ObjectType object, ReturnValue &return_value) {
+    SharedRealm& realm = *get_internal<T, RealmClass<T>>(object);
+    bool is_empty = ObjectStore::is_empty(realm->read_group());
+    return_value.set(is_empty);
+}
+
 template<typename T>
 void RealmClass<T>::get_path(ContextType ctx, ObjectType object, ReturnValue &return_value) {
     std::string path = get_internal<T, RealmClass<T>>(object)->get()->config().path;
diff --git a/tests/js/realm-tests.js b/tests/js/realm-tests.js
index 7ec5c8dd..a2c335e0 100644
--- a/tests/js/realm-tests.js
+++ b/tests/js/realm-tests.js
@@ -932,5 +932,16 @@ module.exports = {
             var p3 = realm.create('PersonObject', { name: 'Wendy', age: 52, children: p2.children });
             TestCase.assertEqual(p3.children.length, 1);
         });
+    },
+
+    testEmpty: function() {
+        const realm = new Realm({schema: [schemas.PersonObject]});
+        TestCase.assertTrue(realm.empty);
+
+        realm.write(() => realm.create('PersonObject', { name: 'Ari', age: 10 }));
+        TestCase.assertTrue(!realm.empty);
+
+        realm.write(() => realm.delete(realm.objects('PersonObject')));
+        TestCase.assertTrue(realm.empty);
     }
 };