datastore: support kind schema. fixes googleapis#85 googleapis#86

lib/datastore/dataset.js

@@ -129,6 +129,64 @@ Dataset.prototype.key = function(keyConfig) {
   return new entity.Key(keyConfig);
 };
 
+/**
+ * Register a Kind's schema. You can later refer to the schema to validate an
+ * entity. See `validateKind` for an example.
+ *
+ * @param {string} kind - Name of the kind.
+ * @param {object} schema - Schema to register to the kind.
+ *
+ * @example
+ * ds.registerKind('Person', {
+ *   name: {
+ *     type: String
+ *   },
+ *   age: {
+ *     type: datastore.int
+ *   }
+ * });
+ */
+Dataset.prototype.registerKind = function(kind, schema) {
+  var namespace = this.namespace;
+  if (util.is(kind, 'object')) {
+    namespace = kind.namespace;
+    schema = kind.schema;
+    kind = kind.name;
+  }
+  entity.registerKind(namespace, kind, schema);
+};
+
+/**
+ * Validate a registered Kind's schema against an entity. This can be useful
+ * before saving a new entity to the Datastore.
+ *
+ * @param  {string} kind - Name of the kind.
+ * @param  {object} ent - Object to validate against the kind's schema.
+ * @return {booelan}
+ *
+ * @example
+ * // See how we registered the "Person" schema in the `registerKind` example.
+ *
+ * ds.validateKind('Person', {
+ *   name: 'Abe Vigoda',
+ *   age: datastore.int(93)
+ * });
+ * // true (`name` is a String, and `age` is an integer)
+ *
+ * ds.validateKind('Person', {
+ *   name: 'Abe Vigoda'
+ * });
+ * // false (missing the `age` property)
+ */
+Dataset.prototype.validateKind = function(kind, ent) {
+  var namespace = this.namespace;
+  if (util.is(kind, 'object')) {
+    namespace = kind.namespace;
+    ent = kind.entity;
+    kind = kind.name;
+  }
+  return entity.validateKind(namespace, kind, ent);
+};
 
 /**
  * Create a query from the current dataset to query the specified kinds, scoped