~ubuntu-branches/ubuntu/precise/whoopsie-daisy/precise-updates

Model is a lightweight <a href="../attribute/index.html">Attribute</a>-based data model with methods for getting, setting, validating, and syncing attribute values to a persistence layer or server, as well as events for notifying listeners of model changes.

</p>

<p>

The <code>Y.Model</code> class is intended to be extended by a custom class that defines

custom model attributes, validators, and behaviors.

</p>

</div>

<h2 id="getting-started">Getting Started</h2>

<p>

To include the source files for Model and its dependencies, first load

the YUI seed file if you haven't already loaded it.

</p>

<p>

Next, create a new YUI instance for your application and populate it with the

modules you need by specifying them as arguments to the <code>YUI().use()</code> method.

YUI will automatically load any dependencies required by the modules you

specify.

</p>

// Create a new YUI instance and populate it with the required modules.

YUI().use('model', function (Y) {

// Model is available and ready for use. Add implementation

// code here.

});

</script></pre>

<p>

For more information on creating YUI instances and on the

<a href="http://yuilibrary.com/yui/docs/api/classes/YUI.html#method_use"><code>use()</code> method</a>, see the

documentation for the <a href="../yui/index.html">YUI Global Object</a>.

</p>

<h2 id="what-is-a-model">What is a Model?</h2>

<p>

A model is a class that manages data, state, and behavior associated with an application or a part of an application.

</p>

<p>

For example, in a photo gallery, you might use a model to represent each photo. The model would contain information about the image file, a caption, tags, etc., along with methods for working with this data. The model would also be responsible for validating any new data before accepting it.

</p>

<p>

While Model may be used as a standalone component, it's common to associate a Model instance with a <a href="../view/index.html">View</a> instance, which is responsible for rendering the visual representation of the data contained in the model and updating that representation when the model changes.

</p>

<h2 id="using-model">Using Model</h2>

<h3 id="quick-start">Quick Start</h3>

<p>

The quickest way to get up and running with Model is to create a new instance of the <code>Y.Model</code> class and pass in an object of key/value pairs representing attributes to set (note: creating ad-hoc attributes like this requires YUI 3.5.0 or higher).

</p>

<p>

Here's how you might create a simple model representing a delicious pie (imagine you're building an online ordering system for a bakery):

</p>

<pre class="code prettyprint">var applePie = new Y.Model({

slices: 6, // number of slices in this pie

type : 'apple' // what type of pie this is

});</pre>

100

<p>

101

This creates a new <code>Y.Model</code> instance named <code>applePie</code>, with two attributes: <code>slices</code> and <code>type</code>, in addition to the <a href="#built-in-attributes">built-in attributes</a> <code>id</code> and <code>clientId</code>, which are available on all models.

102

</p>

103

104

<p>

105

Pass the name of an attribute to the model's <code>get()</code> function to get that attribute's value.

106

</p>

107

108

<pre class="code prettyprint">applePie.get('slices'); // => 6

109

applePie.get('type'); // => "apple"</pre>

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111

112

<p>

113

To change the value of an attribute, pass its name and new value to <code>set()</code>.

114

</p>

115

116

<pre class="code prettyprint">applePie.set('slices', 5); // someone ate a slice!</pre>

117

118

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<p>

120

Read on to learn how to create custom model subclasses for representing more complex data and logic, or skip ahead to <a href="#model-events">Model Events</a> or <a href="#getting-and-setting-attribute-values">Getting and Setting Attribute Values</a> to learn more about how to take advantage of the useful state management functionality Model provides.

121

</p>

122

123

<h3 id="extending-ymodel">Extending <code>Y.Model</code></h3>

124

125

<p>

126

The ability to create ad-hoc models by instantiating <code>Y.Model</code> is convenient, but sometimes it can be useful to create a custom Model subclass by <em>extending</em> <code>Y.Model</code>. This allows you to declare the data attributes your Model class will manage up front, as well as specify default attribute values, helper methods, validators, and (optionally) a sync layer to help your Model class communicate with a storage API or a remote server.

127

</p>

128

129

<p>

130

In this example, we'll create a <code>Y.PieModel</code> class. Each instance of this class will represent a delicious pie, fresh from the oven.

131

</p>

132

133

<pre class="code prettyprint">// Create a new Y.PieModel class that extends Y.Model.

134

Y.PieModel = Y.Base.create('pieModel', Y.Model, [], {

135

// Add prototype methods for your Model here if desired. These methods will be

136

// available to all instances of your Model.

137

138

// Returns true if all the slices of the pie have been eaten.

139

allGone: function () {

140

return this.get('slices') === 0;

141

142

143

// Consumes a slice of pie, or fires an `error` event if there are no slices

144

// left.

145

eatSlice: function () {

146

if (this.allGone()) {

147

this.fire('error', {

148

type : 'eat',

149

error: "Oh snap! There isn't any pie left."

150

});

151

} else {

152

this.set('slices', this.get('slices') - 1);

153

Y.log('You just ate a slice of delicious ' + this.get('type') + ' pie!');

154

}

155

}

156

}, {

157

ATTRS: {

158

// Add custom model attributes here. These attributes will contain your

159

// model's data. See the docs for Y.Attribute to learn more about defining

160

// attributes.

161

162

slices: {

163

value: 6 // default value

164

165

166

type: {

167

value: 'apple'

168

}

169

}

170

});</pre>

171

172

173

<p>

174

Now we can create instances of <code>Y.PieModel</code> to represent delicious pies.

175

</p>

176

177

<p>

178

Each instance will have a <code>type</code> attribute containing the type of the pie and a <code>slices</code> attribute containing the number of slices remaining. We can call the <code>allGone()</code> method to check whether there are any slices left, and the <code>eatSlice()</code> method to eat a slice.

179

</p>

180

181

<pre class="code prettyprint">// Bake a delicious new pecan pie.

182

var pecanPie = new Y.PieModel({type: 'pecan'});

183

184

pecanPie.on('error', function (e) {

185

Y.log(e.error);

186

});

187

188

pecanPie.eatSlice(); // => "You just ate a slice of delicious pecan pie!"

189

Y.log(pecanPie.get('slices')); // => 5</pre>

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191

192

<p>

193

Five slices later, our pie will be all gone. If we try to eat another slice, we'll get an <code>error</code> event.

194

</p>

195

196

<pre class="code prettyprint">// 5 slices later...

197

pecanPie.eatSlice(); // => "Oh snap! There isn't any pie left."</pre>

198

199

200

<h3 id="model-attributes">Model Attributes</h3>

201

202

<p>

203

A Model's data is represented by <a href="../attribute/index.html">attributes</a>. The Model class provides two built-in attributes, <code>clientId</code> and <code>id</code>. The rest are up to you to define when you extend <code>Y.Model</code>.

204

</p>

205

206

<h4 id="built-in-attributes">Built-in Attributes</h4>

207

208

<table>

209

<thead>

210

<tr>

211

<th>Attribute</th>

212

<th>Default Value</th>

213

<th>Description</th>

214

</tr>

215

</thead>

216

<tbody>

217

<tr>

218

<td><code>clientId</code></td>

219

<td><em>generated id</em></td>

220

<td>

221

<p>

222

An automatically generated client-side only unique ID for identifying model instances that don't yet have an <code>id</code>. The client id is guaranteed to be unique among all models on the current page, but is not unique across pageviews. Client ids are never included in <code>toJSON()</code> output.

223

</p>

224

</td>

225

</tr>

226

227

<tr>

228

229

230

<td>

231

<p>

232

A globally unique identifier for the model instance. If this is <code>null</code>, then the model instance is assumed to be "new" (meaning it hasn't yet been saved to a persistence layer). If the model represents data that's stored in a database of some kind, it usually makes sense to use the database's primary key here.

233

</p>

234

235

<p>

236

If your persistence layer uses a primary key with a name other than <code>id</code>, you can override the <code>idAttribute</code> property and set it to the name of your custom id attribute when extending <code>Y.Model</code> (be sure to define a corresponding attribute as well). The <code>id</code> attribute will then act as an alias for your custom id attribute.

237

</p>

238

</td>

239

</tr>

240

</tbody>

241

</table>

242

243

<h4 id="custom-attributes">Custom Attributes</h4>

244

245

<p>

246

Custom attributes are where all your model's data should live. You define these attributes when you first extend <code>Y.Model</code>. You can set their values by passing a config object into the model's constructor, or by calling the model's <code>set()</code> or <code>setAttrs()</code> methods..

247

</p>

248

249

<p>

250

Attributes can specify default values, getters and setters, validators, and more. For details, see the documentation for the <a href="../attribute/index.html">Attribute</a> component.

251

</p>

252

253

<h3 id="model-properties">Model Properties</h3>

254

255

<p>

256

The following properties are available on Model instances. The <code>idAttribute</code> property may be overridden when extending <code>Y.Model</code>; the others are intended to be read-only.

257

</p>

258

259

<table>

260

<thead>

261

<tr>

262

<th>Property</th>

263

264

<th>Description</th>

265

</tr>

266

</thead>

267

<tbody>

268

<tr>

269

<td><code>changed</code></td>

270

<td>Object</td>

271

<td>

272

<p>

273

Hash of attributes that have changed since the last time the model was saved.

274

</p>

275

</td>

276

</tr>

277

278

<tr>

279

<td><code>idAttribute</code></td>

280

<td>String</td>

281

<td>

282

<p>

283

Name of the attribute to use as the unique id for the model. Defaults to "id", but you may override this property when extending <code>Y.Model</code> if you want to specify a custom id attribute.

284

</p>

285

</td>

286

</tr>

287

288

<tr>

289

<td><code>lastChange</code></td>

290

<td>Object</td>

291

<td>

292

<p>

293

Hash of attributes that were changed in the most recent <code>change</code> event. Each item in this hash is an object with the following properties:

294

</p>

295

296

297

<dt><strong><code>newVal</code></strong></dt>

298

<dd>

299

<p>

300

The new value of the attribute after it changed.

301

</p>

302

</dd>

303

304

<dt><strong><code>prevVal</code></strong></dt>

305

<dd>

306

<p>

307

The old value of the attribute before it changed.

308

</p>

309

</dd>

310

311

312

<dd>

313

<p>

314

The source of the change, or <code>null</code> if no source was specified when the change was made.

315

</p>

316

317

<p>

318

This can be set to any string you want by passing an options object like <code>{src: 'foo'}</code> to the <code>set()</code> or <code>setAttrs()</code> methods when changing attribute values. Its purpose is to allow you to identify the source of the change later by inspecting the <code>src</code> property associated with an event, so choose a string that has meaning for your particular use case.

319

</p>

320

</dd>

321

</dl>

322

</td>

323

</tr>

324

325

<tr>

326

<td><code>lists</code></td>

327

<td>Array</td>

328

<td>

329

<p>

330

Array of <a href="../model-list/index.html">ModelList</a> instances that contain this model.

331

</p>

332

333

<p>

334

This property is updated automatically when the model is added to or removed from a ModelList instance. You shouldn't alter it manually. When working with models in a list, you should always add and remove models using the list's <code>add()</code> and <code>remove()</code> methods.

335

</p>

336

</td>

337

</tr>

338

</tbody>

339

</table>

340

341

<h3 id="model-events">Model Events</h3>

342

343

<p>

344

Model instances provide the following events:

345

</p>

346

347

<table>

348

<thead>

349

<tr>

350

<th>Event</th>

351

352

<th>Payload</th>

353

</tr>

354

</thead>

355

<tbody>

356

<tr>

357

<td><code>change</code></td>

358

<td>

359

<p>

360

One or more attributes on the model are changed.

361

</p>

362

</td>

363

<td>

364

<dl>

365

<dt><code>changed</code> (<em>Object</em>)</dt>

366

<dd>

367

<p>

368

Hash of change information for each attribute that changed. Keys are attribute names, values are objects with the following properties:

369

</p>

370

371

372

<dt><code>newVal</code></dt>

373

<dd>

374

<p>

375

The new value of the attribute after it changed.

376

</p>

377

</dd>

378

379

<dt><code>prevVal</code></dt>

380

<dd>

381

<p>

382

The old value of the attribute before it changed.

383

</p>

384

</dd>

385

386

387

<dd>

388

<p>

389

The source of the change, or <code>null</code> if no source was specified when the change was made.

390

</p>

391

392

<p>

393

394

</p>

395

</dd>

396

</dl>

397

</dd>

398

</dl>

399

</td>

400

</tr>

401

402

<tr>

403

<td><code>error</code></td>

404

<td>

405

<p>

406

An error occurs, such as when the model fails validation or a sync layer response can't be parsed.

407

</p>

408

</td>

409

<td>

410

<dl>

411

<dt><code>error</code></dt>

412

<dd>

413

<p>

414

Error message, object, or exception generated by the error. Calling <code>toString()</code> on this should result in a meaningful error message.

415

</p>

416

</dd>

417

418

419

<dd>

420

<p>

421

Source of the error. May be one of the following default sources, or any custom error source used by your Model subclass):

422

</p>

423

424

425

426

<dd>

427

<p>

428

An error loading the model from a sync layer. The sync layer's response (if any) will be provided as the <code>response</code> property on the event facade.

429

</p>

430

</dd>

431

432

<dt><code>parse</code></dt>

433

<dd>

434

<p>

435

An error parsing a response from a sync layer.

436

</p>

437

</dd>

438

439

440

<dd>

441

<p>

442

An error saving the model to a sync layer. The sync layer's response (if any) will be provided as the <code>response</code> property on the event facade.

443

</p>

444

</dd>

445

446

<dt><code>validate</code></dt>

447

<dd>

448

<p>

449

The model failed to validate.

450

</p>

451

</dd>

452

</dl>

453

</dd>

454

</dl>

455

</td>

456

</tr>

457

458

<tr>

459

460

<td>

461

<p>

462

After model attributes are loaded from a sync layer.

463

</p>

464

</td>

465

<td>

466

<dl>

467

<dt><code>parsed</code></dt>

468

<dd>

469

<p>

470

The parsed version of the sync layer's response to the load request.

471

</p>

472

</dd>

473

474

<dt><code>response</code></dt>

475

<dd>

476

<p>

477

The sync layer's raw, unparsed response to the load request.

478

</p>

479

</dd>

480

</dl>

481

</td>

482

</tr>

483

484

<tr>

485

486

<td>

487

<p>

488

After model attributes are saved to a sync layer.

489

</p>

490

</td>

491

<td>

492

<dl>

493

<dt><code>parsed</code></dt>

494

<dd>

495

<p>

496

The parsed version of the sync layer's response to the save request.

497

</p>

498

</dd>

499

500

<dt><code>response</code></dt>

501

<dd>

502

<p>

503

The sync layer's raw, unparsed response to the save request.

504

</p>

505

</dd>

506

</dl>

507

</td>

508

</tr>

509

</tbody>

510

</table>

511

512

<p>

513

A model's events bubble up to any <a href="../model-list/index.html">model lists</a> that the model belongs to. This enables you to use the model list as a central point for handling model value changes and errors.

514

</p>

515

516

<h4 id="change-events">Change Events</h4>

517

518

<p>

519

In addition to the master <code>change</code> event, which is fired whenever one or more attributes are changed, there are also change events for each individual attribute.

520

</p>

521

522

<p>

523

Attribute-level change events follow the naming scheme <code><em>name</em>Change</code>, where <em>name</em> is the name of an attribute.

524

</p>

525

526

<pre class="code prettyprint">// Bake a new pie model.

527

var pie = new Y.PieModel();

528

529

// Listen for all attribute changes.

530

pie.on('change', function (e) {

531

Y.log('change fired: ' + Y.Object.keys(e.changed).join(', '));

532

});

533

534

// Listen for changes to the `slices` attribute.

535

pie.on('slicesChange', function (e) {

536

Y.log('slicesChange fired');

537

});

538

539

// Listen for changes to the `type` attribute.

540

pie.on('typeChange', function (e) {

541

Y.log('typeChange fired');

542

});

543

544

// Change multiple attributes at once.

545

pie.setAttrs({

546

slices: 3,

547

type : 'maple custard'

548

});

549

550

// => "slicesChange fired"

551

// => "typeChange fired"

552

// => "change fired: slices, type"</pre>

553

554

555

<h4 id="firing-your-own-error-events">Firing Your Own Error Events</h4>

556

557

<p>

558

In your custom model class, there may be situations beyond just parsing and validating in which an <code>error</code> event would be useful. For example, in the <code>Y.PieModel</code> class, we fire an error when someone tries to eat a slice of pie and there are no slices left.

559

</p>

560

561

<pre class="code prettyprint">// Consumes a slice of pie, or fires an `error` event if there are no slices

562

// left.

563

eatSlice: function () {

564

if (this.allGone()) {

565

this.fire('error', {

566

type : 'eat',

567

error: "Oh snap! There isn't any pie left."

568

});

569

} else {

570

this.set('slices', this.get('slices') - 1);

571

Y.log('You just ate a slice of delicious ' + this.get('type') + ' pie!');

572

}

573

}</pre>

574

575

576

<p>

577

When firing an error event, set the <code>type</code> property to something that users of your class can use to identify the type of error that has occurred. In the example above, we set it to "eat", because it occurred when the caller tried to eat a slice of pie.

578

</p>

579

580

<p>

581

The <code>error</code> property should be set to an error message, an Error object, or anything else that provides information about the error and has a <code>toString()</code> method that returns an error message string.

582

</p>

583

584

<h3 id="working-with-model-data">Working with Model Data</h3>

585

586

<h4 id="getting-and-setting-attribute-values">Getting and Setting Attribute Values</h4>

587

588

<p>

589

Model's <code>get()</code> and <code>set()</code> methods are the main ways of interacting with model attributes. Unsurprisingly, they allow you to get and set the value of a single attribute.

590

</p>

591

592

<pre class="code prettyprint">var pie = new Y.PieModel();

593

594

// Set the value of the `type` attribute.

595

pie.set('type', 'banana cream');

596

597

// Get the value of the `type` attribute.

598

pie.get('type'); // => "banana cream"</pre>

599

600

601

<p>

602

Model also provides two convenience methods for getting and escaping an attribute value in a single step. The <code>getAsHTML()</code> method returns an HTML-escaped value, and the <code>getAsURL()</code> method returns a URL-encoded value.

603

</p>

604

605

<pre class="code prettyprint">pie.set('type', 'strawberries & cream');

606

607

pie.getAsHTML('type'); // => "strawberries &amp; cream"

608

pie.getAsURL('type'); // => "strawberries%20%26%20cream"</pre>

609

610

611

<p>

612

The <code>getAttrs()</code> and <code>setAttrs()</code> methods may be used to get and set multiple attributes at once. <code>getAttrs()</code> returns a hash of all attribute values, while <code>setAttrs()</code> accepts a hash of attribute values. When you set multiple attributes with <code>setAttrs()</code>, it fires only a single change event that contains all the affected attributes..

613

</p>

614

615

<pre class="code prettyprint">pie.setAttrs({

616

slices: 6,

617

type : 'marionberry'

618

});

619

620

pie.getAttrs();

621

// => {

622

// clientId: "pieModel_1",

623

// destroyed: false,

624

// id: null,

625

// initialized: true,

626

// slices: 6,

627

// type: "marionberry"

628

// }</pre>

629

630

631

<p>

632

The <code>destroyed</code> and <code>initialized</code> attributes you see in the sample output above are lifecycle attributes provided by <code>Y.Base</code>, and aren't actually model data.

633

</p>

634

635

<p>

636

To get a slightly more useful representation of model data, use the <code>toJSON()</code> method. The <code>toJSON()</code> method excludes the <code>clientId</code>, <code>destroyed</code>, and <code>initialized</code> attributes, making the resulting object more suitable for serialization and for storing in a persistence layer.

637

</p>

638

639

<pre class="code prettyprint">pie.toJSON();

640

// => {

641

// id: null,

642

// slices: 6,

643

// type: "marionberry"

644

// }</pre>

645

646

647

<p>

648

If a custom <code>idAttribute</code> is in use, the <code>toJSON()</code> output will include that id attribute instead of <code>id</code>.

649

</p>

650

651

<pre class="code prettyprint">// toJSON() output with a custom id attribute.

652

pie.toJSON();

653

// => {

654

// customId: null,

655

// slices: 6,

656

// type: "marionberry"

657

// }</pre>

658

659

660

<p>

661

If you'd like to customize the serialized representation of your models, you may override the <code>toJSON()</code> method.

662

</p>

663

664

<p>

665

When using the <code>set()</code> and <code>setAttrs()</code> methods, you may pass an optional <code>options</code> argument. If <code>options.silent</code> is <code>true</code>, no <code>change</code> event will be fired.

666

</p>

667

668

<pre class="code prettyprint">// Set attributes without firing a `change` event.

669

pie.set('slices', 0, {silent: true});

670

671

pie.setAttrs({

672

slices: 0,

673

type : 'chocolate cream'

674

}, {silent: true});</pre>

675

676

677

<p>

678

After making changes to a model's attributes, you may call the <code>undo()</code> method to undo the previous change.

679

</p>

680

681

<pre class="code prettyprint">var pie = new Y.PieModel({slices: 6});

682

683

pie.set('slices', 5);

684

pie.undo();

685

pie.get('slices'); // => 6</pre>

686

687

688

<p>

689

Note that there's only a single level of undo, so it's not possible to revert past the most recent change.

690

</p>

691

692

<h4 id="validating-changes">Validating Changes</h4>

693

694

<p>

695

Validating model changes as they occur is a good way to ensure that the data in your models isn't nonsense, especially when dealing with user input.

696

</p>

697

698

<p>

699

There are two ways to validate model attributes. One way is to define an attribute validator function for an individual attribute when you extend <code>Y.Model</code>.

700

</p>

701

702

<pre class="code prettyprint">// Defining an individual attribute validator.

703

Y.PieModel = Y.Base.create('pieModel', Y.Model, [], {

704

// ... prototype methods and properties ...

705

}, {

706

ATTRS: {

707

slices: {

708

value: 6,

709

validator: function (value) {

710

return typeof value === 'number' && value >= 0 && value <= 10;

711

}

712

713

714

// ...

715

}

716

});</pre>

717

718

719

<p>

720

An attribute validator will be called whenever that attribute changes, and can prevent the change from taking effect by returning <code>false</code>. Model <code>error</code> events are not fired when attribute validators fail. For more details on attribute validators, see the <a href="../attribute/index.html">Attribute User Guide</a>.

721

</p>

722

723

<p>

724

The second way to validate changes is to provide a custom <code>validate()</code> method when extending <code>Y.Model</code>. The <code>validate()</code> method will be called automatically when <code>save()</code> is called, and will receive a hash of all the attributes in the model. If the <code>validate()</code> method returns anything other than <code>null</code> or <code>undefined</code>, it will be considered a validation failure, an <code>error</code> event will be fired with the returned value as the error message, and the <code>save()</code> action will be aborted.

725

</p>

726

727

<pre class="code prettyprint">// Defining a model-wide `validator()` method.

728

Y.PieModel = Y.Base.create('pieModel', Y.Model, [], {

729

// ... prototype methods and properties ...

730

731

validate: function (attributes) {

732

var slices;

733

734

switch (attributes.type) {

735

case 'rhubarb':

736

return 'Eww. No. Not allowed.';

737

738

case 'maple custard':

739

slices = Y.Lang.isValue(attributes.slices) ?

740

attributes.slices : this.get('slices');

741

742

if (slices < 10) {

743

return "Making fewer than 10 slices of maple custard pie would be " +

744

"silly, because I'm just going to eat 8 of them as soon as it's " +

745

"out of the oven.";

746

}

747

}

748

}

749

}, {

750

// ... attributes ...

751

});</pre>

752

753

754

<h4 id="loading-and-saving-model-data">Loading and Saving Model Data</h4>

755

756

<p>

757

Calling a model's <code>load()</code> and <code>save()</code> methods will result in a behind-the-scenes call to the model's <code>sync()</code> method specifying the appropriate action.

758

</p>

759

760

<p>

761

The default <code>sync()</code> method does nothing, but by overriding it and providing your own sync layer, you can make it possible to create, read, update, and delete models from a persistence layer or a server. See <a href="#implementing-a-model-sync-layer">Implementing a Model Sync Layer</a> for more details.

762

</p>

763

764

<p>

765

The <code>load()</code> and <code>save()</code> methods each accept two optional parameters: an options object and a callback function. If provided, the options object will be passed to the sync layer, and the callback will be called after the load or save operation is finished. You may provide neither parameter, or just an options object, or just a callback, although if you provide both an options object and a callback, they need to be in that order.

766

</p>

767

768

<p>

769

The callback function will receive two parameters: an error (this parameter will be <code>null</code> or <code>undefined</code> if the operation was successful) and a response (which is the result of calling the model's <code>parse()</code> method with whatever response the sync layer returned).

770

</p>

771

772

<p>

773

The <code>load()</code> method calls <code>sync()</code> with the <code>read</code> action, and automatically updates the model with the response data (by passing it to <code>parse()</code> and then updating attributes based on the hash that <code>parse()</code> returns) before calling the callback.

774

</p>

775

776

<pre class="code prettyprint">var pie = new Y.PieModel({id: 'pie123'});

777

778

// Load a pie model, passing a callback that will run when the model has

779

// been loaded.

780

pie.load(function (err, response) {

781

if (!err) {

782

// Success! The model now contains the loaded data.

783

}

784

});</pre>

785

786

787

<p>

788

The <code>save()</code> method will do one of two things: if the model is new (meaning it doesn't yet have an <code>id</code> value), it will call <code>sync()</code> with the "create" action. If the model is not new, then it will call <code>sync()</code> with the "update" action.

789

</p>

790

791

<p>

792

If the sync layer returns a response, then <code>save()</code> will update the model's attributes with the response data before calling the callback function.

793

</p>

794

795

<pre class="code prettyprint">// Save a pie model, passing a callback that will run when the model has

796

// been saved.

797

pie.save(function (err, response) {

798

if (!err) {

799

// Success! The model has been saved. If the sync layer returned a response,

800

// then the model has also been updated with any new data in the response.

801

}

802

});</pre>

803

804

805

<p>

806

In addition to calling the specified callback (if any), the <code>load()</code> and <code>save()</code> methods will fire a <code>load</code> event and a <code>save</code> event respectively on success, or an <code>error</code> event on failure. See <a href="#model-events">Model Events</a> for more details on these events.

807

</p>

808

809

<p>

810

Always use the <code>load()</code> or <code>save()</code> methods rather than calling <code>sync()</code> directly, since this ensures that the sync layer's response is passed through the <code>parse()</code> method and that the model's data is updated if necessary.

811

</p>

812

813

<h2 id="the-model-lifecycle">The Model Lifecycle</h2>

814

815

<p>

816

When a model is first created and doesn't yet have an <code>id</code> value, it's considered "new". The <code>isNew()</code> method will tell you whether or not a model is new.

817

</p>

818

819

<p>

820

Once a model has an <code>id</code> value, either because one was manually set or because the model received one when it was loaded or saved, the model is no longer considered new, since it is assumed to exist in a persistence layer or on a server somewhere.

821

</p>

822

823

<p>

824

If a model is new or if any of its attributes have changed since the model was last loaded or saved, the model is considered "modified". The <code>isModified()</code> method will tell you whether or not a model is modified. A successful call to <code>load()</code> or <code>save()</code> will reset a model's "modified" flag.

825

</p>

826

827

<p>

828

Finally, a model's <code>destroy()</code> method can be used to destroy the model instance. Calling <code>destroy()</code> with no arguments will destroy only the local model instance, while calling <code>destroy({remove: true})</code> will both destroy the local model instance and call the sync layer with the "delete" action to delete the model from a persistence layer or server.

829

</p>

830

831

<p>

832

It's not necessary for a model to support all possible sync actions. A model that's used to represent read-only data might use a sync layer that only implements the <code>read</code> action, for instance. In this case, the other actions should simply be no-ops that either call the sync callback immediately, or pass an error to the sync callback indicating that the action isn't supported (depending on your personal preference).

833

</p>

834

835

<h2 id="implementing-a-model-sync-layer">Implementing a Model Sync Layer</h2>

836

837

<p>

838

A model's <code>save()</code>, <code>load()</code>, and <code>destroy()</code> methods all internally call the model's <code>sync()</code> method to carry out an action. The default <code>sync()</code> method doesn't actually do anything, but by overriding the <code>sync()</code> method, you can provide a custom sync layer.

839

</p>

840

841

<p>

842

A sync layer might make Ajax requests to a remote server, or it might act as a wrapper around local storage, or any number of other things.

843

</p>

844

845

<h3 id="the-sync-method">The <code>sync()</code> Method</h3>

846

847

<p>

848

When the <code>sync()</code> method is called, it receives three arguments:

849

</p>

850

851

<dl>

852

<dt><strong><code>action</code> (<em>String</em>)</strong></dt>

853

<dd>

854

<p>

855

A string that indicates the intended sync action. May be one of the following values:

856

</p>

857

858

<dl>

859

<dt><strong><code>create</code></strong></dt>

860

<dd>

861

<p>

862

Create a new model record. The "create" action occurs when a model is saved and doesn't yet have an <code>id</code> value.

863

</p>

864

</dd>

865

866

867

<dd>

868

<p>

869

Read an existing model record. The record should be identified based on the <code>id</code> attribute of the model.

870

</p>

871

</dd>

872

873

<dt><strong><code>update</code></strong></dt>

874

<dd>

875

<p>

876

Update an existing model record. The "update" action occurs when a model is saved and already has an <code>id</code> value. The record to be updated should be identified based on the <code>id</code> attribute of the model.

877

</p>

878

</dd>

879

880

<dt><strong><code>delete</code></strong></dt>

881

<dd>

882

<p>

883

Delete an existing model record. The record to be deleted should be identified based on the <code>id</code> attribute of the model.

884

</p>

885

</dd>

886

</dl>

887

</dd>

888

889

<dt><strong><code>options</code> (<em>Object</em>)</strong></dt>

890

<dd>

891

<p>

892

A hash containing any options that were passed to the <code>save()</code>, <code>load()</code> or <code>destroy()</code> method. This may be used to pass custom options to a sync layer.

893

</p>

894

</dd>

895

896

<dt><strong><code>callback</code> (<em>Function</em>)</strong></dt>

897

<dd>

898

<p>

899

A callback function that should be called when the sync operation is complete. The callback expects to receive the following arguments:

900

</p>

901

902

<dl>

903

904

<dd>

905

<p>

906

Error message or object if an error occured, <code>null</code> or <code>undefined</code> if the operation was successful.

907

</p>

908

</dd>

909

910

<dt><strong><code>response</code></strong></dt>

911

<dd>

912

<p>

913

Response from the persistence layer, if any. This will be passed to the <code>parse()</code> method to be parsed.

914

</p>

915

</dd>

916

</dl>

917

</dd>

918

</dl>

919

920

<p>

921

Implementing a sync layer is as simple as handling the requested sync action and then calling the callback function. Here's a sample sync layer that stores records in local storage (note: this example requires the <code>json-stringify</code> module):

922

</p>

923

924

<pre class="code prettyprint">Y.PieModel = Y.Base.create('pieModel', Y.Model, [], {

925

// ... prototype methods and properties ...

926

927

// Custom sync layer.

928

sync: function (action, options, callback) {

929

var data;

930

931

switch (action) {

932

case 'create':

933

data = this.toJSON();

934

935

// Use the current timestamp as an id just to simplify the example. In a

936

// real sync layer, you'd want to generate an id that's more likely to

937

// be globally unique.

938

data.id = Y.Lang.now();

939

940

// Store the new record in localStorage, then call the callback.

941

localStorage.setItem(data.id, Y.JSON.stringify(data));

942

callback(null, data);

943

return;

944

945

case 'read':

946

// Look for an item in localStorage with this model's id.

947

data = localStorage.getItem(this.get('id'));

948

949

if (data) {

950

callback(null, data);

951

} else {

952

callback('Model not found.');

953

}

954

955

return;

956

957

case 'update':

958

data = this.toJSON();

959

960

// Update the record in localStorage, then call the callback.

961

localStorage.setItem(this.get('id'), Y.JSON.stringify(data));

962

callback(null, data);

963

return;

964

965

case 'delete':

966

localStorage.removeItem(this.get('id'));

967

callback();

968

return;

969

970

default:

971

callback('Invalid action');

972

}

973

}

974

}, {

975

// ... attributes ...

976

});</pre>

977

978

979

<h3 id="the-parse-method">The <code>parse()</code> Method</h3>

980

981

<p>

982

Depending on the kind of response your sync layer returns, you may need to override the <code>parse()</code> method as well. The default <code>parse()</code> implementation knows how to parse JavaScript objects and JSON strings that can be parsed into JavaScript objects representing a hash of attributes. If your response data is in another format, such as a nested JSON response or XML, override the <code>parse()</code> method to provide a custom parser implementation.

983

</p>

984

985

<p>

986

If an error occurs while parsing a response, fire an <code>error</code> event with <code>type</code> "parse".

987

</p>

988

989

<p>

990

This sample demonstrates a custom parser for responses in which the model data is contained in a <code>data</code> property of the response object.

991

</p>

992

993

<pre class="code prettyprint">// Custom response parser.

994

parse: function (response) {

995

if (response.data) {

996

return response.data;

997

}

998

999

this.fire('error', {

1000

type : 'parse',

1001

error: 'No data in the response.'

1002

});

1003

}</pre>

1004

1005

</div>

1006

</div>

1007

</div>

1008

1009

1010

1011

1012

1013

1014

<h2 class="no-toc">Table of Contents</h2>

1015

</div>

1016

1017

1018

1019

<li>

1020

<a href="#getting-started">Getting Started</a>

1021

</li>

1022

<li>

1023

<a href="#what-is-a-model">What is a Model?</a>

1024

</li>

1025

<li>

1026

<a href="#using-model">Using Model</a>

1027

1028

<li>

1029

<a href="#quick-start">Quick Start</a>

1030

</li>

1031

<li>

1032

<a href="#extending-ymodel">Extending <code>Y.Model</code></a>

1033

</li>

1034

<li>

1035

<a href="#model-attributes">Model Attributes</a>

1036

1037

<li>

1038

<a href="#built-in-attributes">Built-in Attributes</a>

1039

</li>

1040

<li>

1041

<a href="#custom-attributes">Custom Attributes</a>

1042

</li>

1043

</ul>

1044

</li>

1045

<li>

1046

<a href="#model-properties">Model Properties</a>

1047

</li>

1048

<li>

1049

<a href="#model-events">Model Events</a>

1050

1051

<li>

1052

<a href="#change-events">Change Events</a>

1053

</li>

1054

<li>

1055

<a href="#firing-your-own-error-events">Firing Your Own Error Events</a>

1056

</li>

1057

</ul>

1058

</li>

1059

<li>

1060

<a href="#working-with-model-data">Working with Model Data</a>

1061

1062

<li>

1063

<a href="#getting-and-setting-attribute-values">Getting and Setting Attribute Values</a>

1064

</li>

1065

<li>

1066

<a href="#validating-changes">Validating Changes</a>

1067

</li>

1068

<li>

1069

<a href="#loading-and-saving-model-data">Loading and Saving Model Data</a>

1070

</li>

1071

</ul>

1072

</li>

1073

</ul>

1074

</li>

1075

<li>

1076

<a href="#the-model-lifecycle">The Model Lifecycle</a>

1077

</li>

1078

<li>

1079

<a href="#implementing-a-model-sync-layer">Implementing a Model Sync Layer</a>

1080

1081

<li>

1082

<a href="#the-sync-method">The <code>sync()</code> Method</a>

1083

</li>

1084

<li>

1085

<a href="#the-parse-method">The <code>parse()</code> Method</a>

1086

</li>

1087

</ul>

1088

</li>

1089

</ul>

1090

</div>

1091

</div>

1092

1093

1094

1095

1096

1097

1098

1099

<h2 class="no-toc">Examples That Use This Component</h2>

1100

</div>

1101

1102

1103

1104

1105

1106

1107

1108

</li>

1109

1110

1111

1112

1113

<a href="../app/app-contributors.html">GitHub Contributors</a>

1114

</li>

1115

1116

1117

</ul>

1118

</div>

1119

</div>

1120

1121

</div>

1122

</div>

1123

</div>

1124

</div>

1125

1126

1127

1128

1129

</body>

1130

</html>

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