config inMemory (#280)

* InMemory implemented in Configuration - Fixes #91 

* InMemory tests added to configuration_test

* CHANGELOG updated

CHANGELOG.md

@@ -10,6 +10,7 @@ x.x.x Release notes (yyyy-MM-dd)
 * Added support checking if Realm lists and Realm objects are valid. ([#183](https://github.com/realm/realm-dart/pull/183))
 * Support query on lists of realm objects. ([#239](https://github.com/realm/realm-dart/pull/239))
 * Added support for opening Realm in read-only mode. ([#260](https://github.com/realm/realm-dart/pull/260))
+* Added support for opening in-memory Realms. ([#280](https://github.com/realm/realm-dart/pull/280))
 * Primary key fields no longer required to be `final` in data model classes ([#240](https://github.com/realm/realm-dart/pull/240))
 * List fields no longer required to be `final` in data model classes. ([#253](https://github.com/realm/realm-dart/pull/253))
 

lib/src/configuration.dart

@@ -36,17 +36,20 @@ class Configuration {
   RealmSchema get schema => _schema;
 
   /// Creates a [Configuration] with schema objects for opening a [Realm].
-  /// [readOnly] controls whether a [Realm] is opened as readonly.
-  /// This allows opening it from locked locations such as resources,
-  /// bundled with an application.  The realm file must already exists.
-  Configuration(List<SchemaObject> schemaObjects, {bool readOnly = false})
+  ///
+  /// [readOnly] controls whether a [Realm] is opened as read-only.
+  /// [inMemory] specifies if a [Realm] should be opened in-memory.
+  Configuration(List<SchemaObject> schemaObjects, {bool readOnly = false, bool inMemory = false})
       : _schema = RealmSchema(schemaObjects),
         _handle = realmCore.createConfig() {
     schemaVersion = 0;
     path = defaultPath;
     if (readOnly) {
       isReadOnly = true;
     }
+    if (inMemory) {
+      isInMemory = true;
+    }
     realmCore.setSchema(this);
   }
 
@@ -97,6 +100,15 @@ class Configuration {
   /// The realm file must already exists at [path]
   bool get isReadOnly => realmCore.getConfigReadOnly(this);
   set isReadOnly(bool value) => realmCore.setConfigReadOnly(this, value);
+
+  /// Specifies if a [Realm] should be opened in-memory.
+  ///
+  /// This still requires a [path] (can be the default path) to identify the [Realm] so other processes can open the same [Realm].
+  /// The file will also be used as swap space if the [Realm] becomes bigger than what fits in memory,
+  /// but it is not persistent and will be removed when the last instance is closed.
+  /// When all in-memory instance of [Realm] is closed all data in that [Realm] is deleted.
+  bool get isInMemory => realmCore.getConfigInMemory(this);
+  set isInMemory(bool value) => realmCore.setConfigInMemory(this, value);
 }
 
 /// A collection of properties describing the underlying schema of a [RealmObject].

lib/src/native/realm_core.dart

@@ -163,6 +163,14 @@ class _RealmCore {
     _realmLib.realm_config_set_schema_mode(config.handle._pointer, mode);
   }
 
+  bool getConfigInMemory(Configuration config) {
+    return _realmLib.realm_config_get_in_memory(config.handle._pointer);
+  }
+
+  void setConfigInMemory(Configuration config, bool value) {
+    _realmLib.realm_config_set_in_memory(config.handle._pointer, value);
+  }
+
   ConfigHandle createConfig() {
     final configPtr = _realmLib.realm_config_new();
     return ConfigHandle._(configPtr);

test/configuration_test.dart

@@ -108,4 +108,21 @@ Future<void> main([List<String>? args]) async {
     expect(() => realm.write(() {}), throws<RealmException>("Can't perform transactions on read-only Realms."));
     realm.close();
   });
+
+  test('Configuration inMemory - no files after closing realm', () {
+    Configuration config = Configuration([Car.schema], inMemory: true);
+    var realm = Realm(config);
+    realm.write(() => realm.add(Car('Tesla')));
+    realm.close();
+    expect(Realm.existsSync(config.path), false);
+  });
+
+  test('Configuration inMemory can not be readOnly', () {
+    Configuration config = Configuration([Car.schema], inMemory: true);
+    var realm = Realm(config);
+
+    config.isReadOnly = true;
+    expect(() => Realm(config), throws<RealmException>("Realm at path '${config.path}' already opened with different read permissions"));
+    realm.close();
+  });
 }