Merge pull request #1442 from nockawa/master

Scene: adding read-only uid property and externalData api

src/babylon.scene.ts

@@ -552,6 +552,9 @@
 
         private _pickedDownMesh: AbstractMesh;
         private _pickedDownSprite: Sprite;
+        private _externalData: StringDictionary<Object>;
+        private _uid: string;
+
 
         /**
          * @constructor
@@ -562,6 +565,9 @@
 
             engine.scenes.push(this);
 
+            this._externalData = new StringDictionary<Object>();
+            this._uid = null;
+
             this._renderingManager = new RenderingManager(this);
 
             this.postProcessManager = new PostProcessManager(this);
@@ -1868,6 +1874,56 @@
             return (this._activeMeshes.indexOf(mesh) !== -1);
         }
 
+        /**
+         * Return a unique id as a string which can serve as an identifier for the scene
+         */
+        public get uid(): string {
+            if (!this._uid) {
+                this._uid = Tools.RandomId();
+            }
+            return this._uid;
+        }
+
+        /**
+         * Add an externaly attached data from its key.
+         * This method call will fail and return false, if such key already exists.
+         * If you don't care and just want to get the data no matter what, use the more convenient getOrAddExternalDataWithFactory() method.
+         * @param key the unique key that identifies the data
+         * @param data the data object to associate to the key for this Engine instance
+         * @return true if no such key were already present and the data was added successfully, false otherwise
+         */
+        public addExternalData<T>(key: string, data: T): boolean {
+            return this._externalData.add(key, data);
+        }
+
+        /**
+         * Get an externaly attached data from its key
+         * @param key the unique key that identifies the data
+         * @return the associated data, if present (can be null), or undefined if not present
+         */
+        public getExternalData<T>(key: string): T {
+            return <T>this._externalData.get(key);
+        }
+
+        /**
+         * Get an externaly attached data from its key, create it using a factory if it's not already present
+         * @param key the unique key that identifies the data
+         * @param factory the factory that will be called to create the instance if and only if it doesn't exists
+         * @return the associated data, can be null if the factory returned null.
+         */
+        public getOrAddExternalDataWithFactory<T>(key: string, factory: (k: string) => T): T {
+            return <T>this._externalData.getOrAddWithFactory(key, factory);
+        }
+
+        /**
+         * Remove an externaly attached data from the Engine instance
+         * @param key the unique key that identifies the data
+         * @return true if the data was successfully removed, false if it doesn't exist
+         */
+        public removeExternalData(key): boolean {
+            return this._externalData.remove(key);
+        }
+
         private _evaluateSubMesh(subMesh: SubMesh, mesh: AbstractMesh): void {
             if (mesh.alwaysSelectAsActiveMesh || mesh.subMeshes.length === 1 || subMesh.isInFrustum(this._frustumPlanes)) {
                 var material = subMesh.getMaterial();