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Marionette.LayoutView

A LayoutView is a hybrid of an ItemView and a collection of Region objects. They are ideal for rendering application layouts with multiple sub-regions managed by specified region managers.

A layoutView can also act as a composite-view to aggregate multiple views and sub-application areas of the screen allowing applications to attach multiple region managers to dynamically rendered HTML.

You can create complex views by nesting layoutView managers within Regions.

For a more in-depth discussion on LayoutViews, see the blog post Manage Layouts And Nested Views With Marionette

Please see the Marionette.ItemView documentation for more information on available features and functionality.

Additionally, interactions with Marionette.Region will provide features such as onShow callbacks, etc. Please see the Region documentation for more information.

Documentation Index

Basic Usage

The LayoutView extends directly from ItemView and adds the ability to specify regions which become Region instances that are attached to the layoutView.

<script id="layout-view-template" type="text/template">
  <section>
    <navigation id="menu">...</navigation>
    <article id="content">...</article>
  </section>
</script>

var AppLayoutView = Marionette.LayoutView.extend({
  template: "#layout-view-template",

  regions: {
    menu: "#menu",
    content: "#content"
  }
});

var layoutView = new AppLayoutView();
layoutView.render();

Once you've rendered the layoutView, you now have direct access to all of the specified regions as region managers.

layoutView.getRegion('menu').show(new MenuView());

layoutView.getRegion('content').show(new MainContentView());

There are also helpful shortcuts for more concise syntax.

layoutView.showChildView('menu', new MenuView());

layoutView.showChildView('content', new MainContentView());

Region Options

A LayoutView can take a regions hash that allows you to specify regions per LayoutView instance.

new Marionette.LayoutView({
 regions: {
   "cat": ".doge",
   "wow": {
     selector: ".such",
     regionClass: Coin
   }
 }
})

LayoutView childEvents

A childEvents hash or method permits handling of child view events without manually setting bindings. The values of the hash can either be a function or a string method name on the collection view.

// childEvents can be specified as a hash...
var MyLayoutView = Marionette.LayoutView.extend({

  childEvents: {
    // This callback will be called whenever a child is rendered or emits a `render` event
    render: function() {
      console.log('A child view has been rendered.');
    }
  }
});

// ...or as a function that returns a hash.
var MyLayoutView = Marionette.LayoutView.extend({

  childEvents: function() {
    return {
      render: this.onChildRender
    }
  },

  onChildRendered: function () {
    console.log('A child view has been rendered.');
  }
});

childEvents also catches custom events fired by a child view. Take note that the first argument to a childEvents handler is the child view itself. Caution: Events triggered on the child view through this.trigger are not yet supported for LayoutView childEvents. Use strictly triggerMethod within the child view.

// The child view fires a custom event, `show:message`
var ChildView = Marionette.ItemView.extend({

  // Events hash defines local event handlers that in turn may call `triggerMethod`.
  events: {
    'click .button': 'onClickButton'
  },

  // Triggers hash converts DOM events directly to view events catchable on the parent.
  triggers: {
    'submit form': 'submit:form'
  },

  onClickButton: function () {
    this.triggerMethod('show:message', 'foo');
  }
});

// The parent uses childEvents to catch that custom event on the child view
var ParentView = Marionette.LayoutView.extend({

  childEvents: {
    'show:message': 'onChildShowMessage',
    'submit:form': 'onChildSubmitForm'
  },

  onChildShowMessage: function (childView, message) {
    console.log('A child view fired show:message with ' + message);
  },

  onChildSubmitForm: function (childView) {
    console.log('A child view fired submit:form');
  }
});

Specifying Regions As A Function

Regions can be specified on a LayoutView using a function that returns an object with the region definitions. The returned object follow the same rules for defining a region, as outlined above.

Marionette.LayoutView.extend({
  // ...

  regions: function(options){
    return {
      fooRegion: "#foo-element"
    };
  },

  // ...
});

Note that the function receives the view's options arguments that were passed in to the view's constructor. this.options is not yet available when the regions are first initialized, so the options must be accessed through this parameter.

Overriding the default RegionManager

If you need the RegionManager's class chosen dynamically, specify getRegionManager:

Marionette.LayoutView.extend({
  // ...

  getRegionManager: function() {
    // custom logic
    return new MyRegionManager();
  }

This can be useful if you want to attach LayoutView's regions to your own instance of RegionManager.

Region Availability

Any defined regions within a layoutView will be available to the View or any calling code immediately after instantiating the View. This allows a View to be attached to an existing DOM element in an HTML page, without the need to call a render method or anything else, to create the regions.

However, a region will only be able to populate itself if the View has access to the elements specified within the region definitions. That is, if your view has not yet rendered, your regions may not be able to find the element that you've specified for them to manage. In that scenario, using the region will result in no changes to the DOM.

Re-Rendering A LayoutView

A layoutView can be rendered as many times as needed, but renders after the first one behave differently than the initial render.

The first time a layoutView is rendered, nothing special happens. It just delegates to the ItemView prototype to do the render. After the first render has happened, though, the render function is modified to account for re-rendering with regions in the layoutView.

After the first render, all subsequent renders will force every region to be emptied by calling the empty method on them. This will force every view in the region, and sub-views if any, to be destroyed as well. Once the regions are emptied, the regions will also be reset so that they are no longer referencing the element of the previous layoutView render.

Then after the layoutView is finished re-rendering itself, showing a view in the layoutView's regions will cause the regions to attach themselves to the new elements in the layoutView.

Avoid Re-Rendering The Entire LayoutView

There are times when re-rendering the entire layoutView is necessary. However, due to the behavior described above, this can cause a large amount of work to be needed in order to fully restore the layoutView and all of the views that the layoutView is displaying.

Therefore, it is suggested that you avoid re-rendering the entire layoutView unless absolutely necessary. Instead, if you are binding the layoutView's template to a model and need to update portions of the layoutView, you should listen to the model's "change" events and only update the necessary DOM elements.

Nested LayoutViews And Views

Since the LayoutView extends directly from ItemView, it has all of the core functionality of an item view. This includes the methods necessary to be shown within an existing region manager.

In the following example, we will use the Application's Regions as the base of a deeply nested view structure.

// Create an Application
var MyApp = new Marionette.Application();

// Add a region
MyApp.addRegions({
  main: "main"
});

// Create a new LayoutView
var layoutView = new Marionette.LayoutView({
  // This option removes the layoutView from
  // the DOM before destroying the children
  // preventing repaints as each option is removed.
  // However, it makes it difficult to do close animations
  // for a child view (false by default)
  destroyImmediate: true
});

// Lastly, show the LayoutView in the App's mainRegion
MyApp.getRegion('main').show(layoutView);

You can nest LayoutViews as deeply as you want. This provides for a well organized, nested view structure.

For example, to nest 3 layouts:

var layout1 = new Layout1();
var layout2 = new Layout2();
var layout3 = new Layout3();

MyApp.getRegion('main').show(layout1);

layout1.showChildView('region1', layout2);
layout2.showChildView('region2', layout3);

Efficient Nested View Structures

The above example works great, but it causes three separate paints: one for each layout that's being shown. Marionette provides a simple mechanism to infinitely nest views in a single paint: just render all of the children in the onBeforeShow callback.

var ParentLayout = Marionette.LayoutView.extend({
  onBeforeShow: function() {
    this.showChildView('header', new HeaderView());
    this.showChildView('footer', new FooterView());
  }
});

myRegion.show(new ParentLayout());

In this example, the doubly-nested view structure will be rendered in a single paint.

This system is recursive, so it works for any deeply nested structure. The child views you show can render their own child views within their onBeforeShow callbacks!

Use of the attach event

Often times you need to know when your views in the view tree have been attached to the document, like when using certain jQuery plugins. The attach event, and associated onAttach callback, are perfect for this use case. Start with a Region that's a child of the document and show any LayoutView in it: every view in the tree (including the parent LayoutView) will have the attach event triggered on it when they have been attached to the document.

Note that inefficient tree rendering will cause the attach event to be fired multiple times. This situation can occur if you render the children views after the parent has been rendered, such as using onShow to render children. As a rule of thumb, most of the time you'll want to render any nested views in the onBeforeShow callback.

Destroying A LayoutView

When you are finished with a layoutView, you can call the destroy method on it. This will ensure that all of the region managers within the layoutView are destroyed correctly, which in turn ensures all of the views shown within the regions are destroyed correctly.

If you are showing a layoutView within a parent region manager, replacing the layoutView with another view or another layoutView will destroy the current one, the same it will destroy a view.

All of this ensures that layoutViews and the views that they contain are cleaned up correctly.

When calling destroy on a layoutView, the layoutView will be returned. This can be useful for chaining.

Custom Region Class

If you have the need to replace the Region with a region class of your own implementation, you can specify an alternate class to use with the regionClass property of the LayoutView.

var MyLayoutView = Marionette.LayoutView.extend({
  regionClass: SomeCustomRegion
});

You can also specify custom Region classes for each region:

var AppLayoutView = Marionette.LayoutView.extend({
  template: "#layout-view-template",

  regionClass: SomeDefaultCustomRegion,

  regions: {
    menu: {
      selector: "#menu",
      regionClass: CustomRegionClassReference
    },
    content: {
      selector: "#content",
      regionClass: CustomRegionClass2Reference
    }
  }
});

Adding And Removing Regions

Regions can be added and removed as needed, in a LayoutView instance. Use the following methods:

addRegion:

var layoutView = new MyLayoutView();

// ...

layoutView.addRegion("foo", "#foo");
layoutView.getRegion('foo').show(new someView());

addRegions:

var layoutView = new MyLayoutView();

// ...

// Object literal
layoutView.addRegions({
  foo: "#foo",
  bar: "#bar"
});

// Or, function that returns an object literal
layoutView.addRegions(function() {
  return {
    baz: "#baz",
    quux: "#quux"
  };
});

removeRegions:

var layoutView = new MyLayoutView();

// ...

layoutView.removeRegion("foo");

Any region can be removed, whether it was defined in the regions attribute of the region definition, or added later.

For more information on using these methods, see the regionManager documentation.

Region Naming

A LayoutViews' Regions are attached directly to the LayoutView instance with the name of the region as the key and the region itself as the value. Because of this, you need to be careful to avoid conflicts with existing properties on the LayoutView when you name your Region.

The prototype chain of LayoutViews is:

Backbone.View > Marionette.View > Marionette.ItemView > Marionette.LayoutView

Consequently, every property on each of those Classes must be avoided as Region names. The most common issue people run into is trying to name their Region "attributes". Be aware that you are not able to do this.

The following is an abbreviated list of other names that can't be used as Region names. For a more complete list refer to the API documentation for each Class on the prototype chain:

Note: this is a known issue that is flagged for being fixed in v2

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