Merge pull request #21 from scup/dynamic-type-builder

types can be build using builder

Author: albertossilva

README.md

@@ -90,7 +90,36 @@ console.log(fatherInstance.children[0]); //An instance of MyEntity
 console.log(fatherInstance.children[1].toJSON());
 //{ field: 'B', otherField: 3 }
 ```
-
+#### Builder
+When you need to create objects with custom verification like 
+```javascript
+    const elementList = {
+        elements: [{
+          type: 'product',
+          name: true,
+          price:  true
+        }, {
+          type: 'default',
+          isDefault: true
+        }]
+      };
+```
+In such cases you can define a builder as follows:
+```javascript
+class ElementList extends Speck {}
+ElementList.SCHEMA = {
+  elements: {
+    validator: noop,
+    builder: (dataList) => dataList.map(data => {
+      if (data.type === 'product') return new ProductEntity(data);
+      if (data.type === 'default') return new FakeEntityWithBoolean(data);
+    })
+  }
+};
+```
+By defining builder you tell Speck Entity that you take the responsibility of instansitating and 
+returning a new object of the type which suits you the best. 
+This is a powerful concept as it lets users dynamically create new types on the fly.
 #### Clean unexpected values
 ```javascript
 const anotherInstance = new MyEntity({ field: 'myString', fake: 'fake' });

spec/Speck.spec.js

@@ -16,7 +16,8 @@ import {
   FatherWithObjectEntity,
   FakeEntityWithExcludeContext,
   FakeEntityWithIncludeContext,
-  FakeEntityWithCustomValidationWithContext
+  FakeEntityWithCustomValidationWithContext,
+  FakeEntityWithCustomElementList
 } from './fixtures/fakerClasses';
 
 describe('Speck', () => {
@@ -125,6 +126,22 @@ describe('Speck', () => {
   });
 
   describe('children', () => {
+    it('builds Hetrogenerous types in a list automatically', () => {
+      const elementEntity = new FakeEntityWithCustomElementList({
+        elements: [{
+          type: 'product',
+          name: true,
+          price:  true
+        }, {
+          type: 'default',
+          isDefault: true
+        }]
+      });
+      
+      expect(elementEntity.elements[0].constructor).to.equal(ProductEntity);
+      expect(elementEntity.elements[1].constructor).to.equal(FakeEntityWithBoolean);
+  });
+    
     it('builds automatically child entities of array', () => {
       const father = new FatherEntity({
         children: [

spec/fixtures/fakerClasses.js

@@ -24,6 +24,17 @@ function alwaysTruth(){
   return true;
 }
 
+class FakeEntityWithCustomElementList extends Speck {}
+FakeEntityWithCustomElementList.SCHEMA = {
+  elements: {
+    validator: noop,
+    builder: (dataList) => dataList.map(data => {
+      if (data.type === 'product') return new ProductEntity(data);
+      if (data.type === 'default') return new FakeEntityWithBoolean(data);
+    })
+  }
+};
+
 class ProductEntity extends Speck { }
 ProductEntity.SCHEMA = {
   name: alwaysTruth,
@@ -153,5 +164,6 @@ Object.assign(exports, {
   FatherWithObjectEntity,
   FakeEntityWithExcludeContext,
   FakeEntityWithIncludeContext,
-  FakeEntityWithCustomValidationWithContext
+  FakeEntityWithCustomValidationWithContext,
+  FakeEntityWithCustomElementList
 });

src/Speck.js

@@ -1,4 +1,4 @@
-import { get, isNil } from 'lodash';
+import { get, isNil, isFunction } from 'lodash';
 
 const createGetterAndSetter = function (instance, field){
   return {
@@ -46,7 +46,7 @@ class Speck {
 
       newData[field] = isNil(data[field]) ? this.schema[field].defaultValue: data[field];
 
-      if (this.schema[field].type) {
+      if (this.schema[field].type || this.schema[field].builder) {
         newData[field] = this.applyEntityConstructor(this.schema[field], newData[field]);
       }
 
@@ -111,7 +111,7 @@ class Speck {
   applyEntityConstructor(field, data) {
     const Type = field.type;
 
-    if(field.builder) {
+    if(isFunction(field.builder)) {
       return field.builder(data, Type);
     }