Possibility to provide default values for the entity

closes gh-117

Author: smashercosmo

README.md

@@ -262,6 +262,9 @@ const article = new Schema('articles', { assignEntity: function (output, key, va
     output[key] = value;
   }
 }})
+
+// You can specify default values for the entity
+const article = new Schema('articles', { defaults: { likes: 0 } });
 ```
 
 ### `Schema.prototype.define(nestedSchema)`
@@ -302,6 +305,17 @@ slugArticle.getIdAttribute();
 // slug
 ```
 
+### `Schema.prototype.getDefaults()`
+
+Returns the default values of the schema.
+
+```javascript
+const article = new Schema('articles', { defaults: { likes: 0 } });
+
+article.getDefaults();
+// { likes: 0 }
+```
+
 ### `arrayOf(schema, [options])`
 
 Describes an array of the schema passed as argument.

src/EntitySchema.js

@@ -11,6 +11,7 @@ export default class EntitySchema {
     this._getId = typeof idAttribute === 'function' ? idAttribute : x => x[idAttribute];
     this._idAttribute = idAttribute;
     this._meta = options.meta;
+    this._defaults = options.defaults;
   }
 
   getAssignEntity() {
@@ -35,6 +36,10 @@ export default class EntitySchema {
     }
     return this._meta && this._meta[prop];
   }
+  
+  getDefaults() {
+    return this._defaults;
+  }
 
   define(nestedSchema) {
     for (let key in nestedSchema) {

src/index.js

@@ -11,10 +11,11 @@ function defaultAssignEntity(normalized, key, entity) {
 function visitObject(obj, schema, bag, options) {
   const { assignEntity = defaultAssignEntity } = options;
 
-  let normalized = {};
+  const defaults = schema && schema.getDefaults && schema.getDefaults();
+  const schemaAssignEntity = schema && schema.getAssignEntity && schema.getAssignEntity();
+  let normalized = isObject(defaults) ? { ...defaults } : {};
   for (let key in obj) {
     if (obj.hasOwnProperty(key)) {
-      const schemaAssignEntity = schema && schema.getAssignEntity && schema.getAssignEntity();
       const entity = visit(obj[key], schema[key], bag, options);
       assignEntity.call(null, normalized, key, entity, obj, schema);
       if (schemaAssignEntity) {

test/index.js

@@ -86,6 +86,56 @@ describe('normalizr', function () {
     });
   });
 
+  it('can provide default values for a single entity', function () {
+    var article = new Schema('articles', {defaults: {isFavorite: false}}),
+      input;
+
+    input = {
+      id: 1,
+      title: 'Some Article'
+    };
+
+    Object.freeze(input);
+
+    normalize(input, article).should.eql({
+      result: 1,
+      entities: {
+        articles: {
+          1: {
+            id: 1,
+            title: 'Some Article',
+            isFavorite: false
+          }
+        }
+      }
+    });
+  });
+
+  it('does not overwrite the default', function () {
+    var article = new Schema('articles', {defaults: {isFavorite: false}}),
+      input;
+
+    input = {
+      id: 1
+    };
+
+    Object.freeze(input);
+
+    normalize({ id: 2, title: 'foo' }, article);
+
+    normalize(input, article).should.eql({
+      result: 1,
+      entities: {
+        articles: {
+          1: {
+            id: 1,
+            isFavorite: false
+          }
+        }
+      }
+    });
+  });
+
   it('can normalize nested entity and delete an existing key using custom function', function () {
     var article = new Schema('articles'),
         type = new Schema('types'),
@@ -636,6 +686,39 @@ describe('normalizr', function () {
     });
   });
 
+  it('can provide default values for an array', function () {
+    var article = new Schema('articles', {defaults: {isFavorite: false}}),
+      input;
+
+    input = [{
+      id: 1,
+      title: 'Some Article'
+    }, {
+      id: 2,
+      title: 'Other Article'
+    }];
+
+    Object.freeze(input);
+
+    normalize(input, arrayOf(article)).should.eql({
+      result: [1, 2],
+      entities: {
+        articles: {
+          1: {
+            id: 1,
+            title: 'Some Article',
+            isFavorite: false
+          },
+          2: {
+            id: 2,
+            title: 'Other Article',
+            isFavorite: false
+          }
+        }
+      }
+    });
+  });
+
   it('can normalize a polymorphic array with schema attribute', function () {
     var article = new Schema('articles'),
         tutorial = new Schema('tutorials'),