Marionette.View

A View is a view that represents an item to be displayed with a template. This is typically a Backbone.Model, Backbone.Collection, or nothing at all.

Views are also used to build up your application hierarchy - you can easily nest multiple views through the regions attribute.

Note: From Marionette v3.x, Marionette.View replaces Marionette.LayoutView and Marionette.ItemView.

Documentation Index

Rendering a Template
- Set How Template is Attached to the el
Managing an Existing Page
- Setting a template to false
Laying Out Views - Regions
Organizing Your View
- Defining ui
- Accessing UI Elements
  - Referencing UI in events and triggers
Events
Model and Collection Events

Rendering a Template

The Marionette View implements a powerful render method which, given a template, will build your HTML from that template, mixing in model information and any extra template context.

Overriding render If you want to add extra behavior to your view's render, you would be best off doing your logic in the onBeforeRender or onRender handlers.

To render a template, set the template attribute on your view:

var Mn = require('backbone.marionette');
var _ = require('underscore');

var MyView = Mn.View.extend({
  tagName: 'h1',
  template: _.template('Contents')
});

var myView = new MyView();
myView.render();

For more detail on how to render templates, see the Template documentation.

Set How Template is Attached to the `el`

Override the view's attachElContent method to change how the a rendered template is attached to the view's el. This method receives one parameter - the rendered html.

The default implementation of attachElContent is:

attachElContent(html) {
  this.$el.html(html);

  return this;
},

Managing an Existing Page

Marionette is able to manage pre-generated pages - either static or server-generated - and treat them as though they were generated from Marionette.

To use the existing page, set the el to match the existing DOM element:

var Mn = require('backbone.marionette');

var MyView = Mn.View({
  el: '#base-element'
});

new myView();
myView.isRendered(); // true if '#base-element` exists
myView.isAttached(); // true if '#base-element` is in the DOM

Marionette will set the appropriate state of the view.

Setting a `template` to `false`

Setting the template to false allows for the view to create all of the bindings and trigger all view events without re-rendering the el of the view. Any other falsy value will throw an exception.

var Mn = require('backbone.marionette');

var MyView = Mn.View({
  el: '#base-element',
  template: false
});

new myView();
myView.render();

Laying Out Views - Regions

The Marionette.View class lets us manage a hierarchy of views using regions. Regions are a hook point that lets us show views inside views, manage the show/hide lifecycles, and act on events inside the children.

This Section only covers the basics. For more information on regions, see the Regions Documentation.

Regions are ideal for rendering application layouts by isolating concerns inside another view. This is especially useful for independently re-rendering chunks of your application without having to completely re-draw the entire screen every time some data is updated.

Regions can be added to a View at class definition, with regions, or at runtime using addRegion.

When you extend View, we use the regions attribute to point to the selector where the new view will be displayed:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  template: '#tpl-view-with-regions',

  regions: {
    firstRegion: '#first-region',
    secondRegion: '#second-region'
  }
});

If we have the following template:

<script type="x-template/underscore" id="tpl-view-with-regions">
  <div id="first-region"></div>
  <div id="second-region"></div>
  <div id="third-region"></div>
</script>

When we show views in the region, the contents of #first-region and #second-region will be replaced with the contents of the view we show. The value in the regions hash is just a jQuery selector, and any valid jQuery syntax will suffice.

Managing Sub-views

View provides a simple interface for managing sub-views with showChildView and getChildView:

Showing a View

To show a view inside a region, simply call showChildView(region, view). This will handle rendering the view's HTML and attaching it to the DOM for you:

var Mn = require('backbone.marionette');
var SubView = require('./subview');

var MyView = Mn.View.extend({
  template: '#tpl-view-with-regions',

  regions: {
    firstRegion: '#first-region'
  },

  onRender: function() {
    this.showChildView('firstRegion', new SubView());
  }
});

Accessing a Child View

To access the child view of a View - use the getChildView(region) method. This will return the view instance that is current being displayed at that region, or null:

var Mn = require('backbone.marionette');
var SubView = require('./subview');

var MyView = Mn.View.extend({
  template: '#tpl-view-with-regions',

  regions: {
    firstRegion: '#first-region'
  },

  onRender: function() {
    this.showChildView('firstRegion', new SubView());
  },

  onSomeEvent: function() {
    var first = this.getChildView('firstRegion');
    first.doSomething();
  }
});

If no view is available, getChildView returns null.

Detaching a Child View

You can detach a child view from a region through detachChildView(region)


var Mn = require('backbone.marionette');
var SubView = require('./subview');

var MyView = Mn.View.extend({
  template: '#tpl-view-with-regions',

  regions: {
    firstRegion: '#first-region',
    secondRegion: '#second-region'
  },

  onRender: function() {
    this.showChildView('firstRegion', new SubView());
  },

  onMoveView: function() {
    var view = this.detachChildView('firstRegion');
    this.showChildView('secondRegion', view);
  }
});

This is a proxy for region.detachView()

Region Availability

Any defined regions within a View 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.

Efficient Nested View Structures

When your views get some more regions, you may want to think of the most efficient way to render your views. Since manipulating the DOM is performance heavy, it's best practice to render most of your views at once.

Marionette provides a simple mechanism to infinitely nest views in a single paint: just render all of the children in the onRender callback.

var Mn = require('backbone.marionette');

var ParentView = Mn.View.extend({
  onRender: function() {
    this.showChildView('header', new HeaderView());
    this.showChildView('footer', new FooterView());
  }
});

myRegion.show(new ParentView(), options);

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 onRender callbacks!

Listening to Events on Children

Using regions lets you listen to the events that fire on child views - views attached inside a region. This lets a parent view take action depending on what is happening in views it directly owns.

To see more information about events, see the events documentation

Organizing Your View

The View provides a mechanism to name parts of your template to be used throughout the view with the ui attribute. This provides a number of benefits:

Provide a reference to commonly used UI elements
Cache the jQuery selector
Change the selector later in only one place in your view

Defining `ui`

To define your ui hash, just set an object of key to jQuery selectors to the ui attribute of your View:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  template: '#my-template',
  ui: {
    save: '#save-button',
    close: '.close-button'
  }
});

Inside your view, the save and close references will point to the jQuery selectors #save-button and .close-button respectively.

Accessing UI Elements

To get the handles to your UI elements, use the getUI(ui) method:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  template: '#my-template',
  ui: {
    save: '#save-button',
    close: '.close-button'
  },

  onDoSomething: function() {
    var saveButton = this.getUI('save');
    saveButton.addClass('disabled');
    saveButton.attr('disabled', 'disabled');
  }
});

As saveButton here is a jQuery selector, you can call any jQuery methods on it, according to the jQuery documentation.

Referencing UI in `events` and `triggers`

The UI attribute is especially useful when setting handlers in the events and triggers objects - simply use the @ui. prefix:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  template: '#my-template',
  ui: {
    save: '#save-button',
    close: '.close-button'
  },

  events: {
    'click @ui.save': 'handleSave'
  },

  triggers: {
    'click @ui.close': 'close:view'
  },

  handleSave: function() {
    this.model.save();
  }
});

In this example, when the user clicks on #save-button, handleSave will be called. If the user clicks on .close-button, then the event close:view will be fired on MyView.

By prefixing with @ui, we can change the underlying template without having to hunt through our view for every place where that selector is referenced - just update the ui object.

Events

Firing events on views allows you to communicate that something has happened on that view and allowing it to decide whether to act on it or not.

During the create/destroy lifecycle for a View, Marionette will call a number of events on the view being created and attached. You can listen to these events and act on them in two ways:

The typical Backbone manner: view.on('render', function() {})
Overriding the onEvent listener methods: onRender: function() {}

onEvent Listeners

Marionette creates onEvent listeners for all events fired using view.triggerMethod('event') - if there is an onEvent method, Marionette will call it for you. An example:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  onRender: function() {
    console.log("Fired whenever view.triggerMethod('render') is called.");
  },

  onOtherEvent: function(argument) {
    console.log("Fired other:event with '" + argument + "' as an argument");
  }
});

var view = new MyView();

view.triggerMethod('other:event', 'test argument');

This will display in the console: Fired other:event with 'test argument' as an argument

To set up handlers for events, see the rules in the Documentation for Events.

Lifecycle Events

When rendering and showing a View, a number of events will be fired to denote certain stages of the creation, or destruction, lifecycle have been reached. For a full list of events, and how to use them, see the documentation for View lifecycle events.

Binding To User Input

Views can bind custom events whenever users perform some interaction with the DOM. Using the view events and triggers handlers lets us either bind user input directly to an action or fire a generic trigger that may or may not be handled.

Event and Trigger Mapping

The events and triggers attributes bind DOM events to actions to perform on the view. They each take a DOM event key and a mapping to the handler.

We'll cover a simple example:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  events: {
    'click a': 'showModal',
    'click @ui.save': 'saveForm'
  },

  triggers: {
    'click @ui.close': 'cancel:entry'
  },

  ui: {
    save: '.btn-save',
    close: '.btn-cancel'
  },

  showModal: function() {
    console.log('Show the modal');
  },

  saveForm: function() {
    console.log('Save the form');
  }
});

Event listeners are constructed by:

'<dom event> <dom node>': 'listener'

The dom event can be a jQuery DOM event - such as click - or another custom event, such as Bootstrap's show.bs.modal.

The dom node represents a jQuery selector or a ui key prefixed by @.. This must exist inside the view once it has completed rendering. For more information about the ui object, and how it works, see the documentation on ui.

View `events`

The view events attribute binds DOM events to functions or methods on the view. The simplest form is to reference a method on the view:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  events: {
    'click a': 'showModal'
  },

  showModal: function(event) {
    console.log('Show the modal');
  }
});

The DOM event gets passed in as the first argument, allowing you to see any information passed as part of the event.

When passing a method reference, the method must exist on the View.

The events attribute can also directly bind functions:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  events: {
    'click a': function(event) {
      console.log('Show the modal');
    }
  }
});

As when passing a string reference to a view method, the events attribute passes in the event as the argument to the function called.

View `triggers`

The view triggers attribute binds DOM events to Marionette View events that can be responded to at the view or parent level. For more information on events, see the events documentation. This section will just cover how to bind these events to views.

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  triggers: {
    'click a': 'link:clicked'
  },

  onLinkClicked: function(view, event) {
    console.log('Show the modal');
  }
});

When the a tag is clicked here, the link:click event is fired. This event can be listened to using the onEvent Binding technique discussed in the events documentation.

The major benefit of the triggers attribute over events is that triggered events can bubble up to any parent views. For a full explanation of bubbling events and listening to child events, see the event bubbling documentation.

View `triggers` Event Object

Event handlers will receive the triggering view as the first argument and the DOM Event object as the second. It is strongly recommended that View's handle their own DOM event objects. It should be considered a best practice to not utilize the DOM event in external listeners.

By default all trigger events are stopped with preventDefault and stopPropagation methods, but you can manually configure the triggers using a hash instead of event name. The example below triggers an event and prevents default browser behaviour using preventDefault method.

var MyView = Mn.View.extend({
  triggers: {
    'click a': {
      event: 'link:clicked',
      preventDefault: true, // this param is optional and will default to true
      stopPropagation: false
    }
  }
});

The default behavior for calling preventDefault can be changed with the feature flag triggersPreventDefault, and stopPropagation can be changed with the feature flag triggersStopPropagation.

Model and Collection events

The Marionette View can bind to events that occur on attached models and collections - this includes both standard backbone-events and custom events.

Model Events

For example, to listen to a model's events:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  modelEvents: {
    'change:attribute': 'actOnChange'
  },

  actOnChange: function(model, value) {
    console.log('New value: ' + value);
  }
});

The modelEvents attribute passes through all the arguments that are passed to model.trigger('event', arguments).

The modelEvents attribute can also take a function returning an object.

Function Callback

You can also bind a function callback directly in the modelEvents attribute:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  modelEvents: {
    'change:attribute': function() {
      console.log('attribute was changed');
    }
  }
})

Collection Events

Collection events work exactly the same way as modelEvents with their own collectionEvents key:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  collectionEvents: {
    sync: 'actOnSync'
  },

  actOnSync: function(collection) {
    console.log('Collection was synchronised with the server');
  }
});

The collectionEvents attribute can also take a function returning an object.

Just as in modelEvents, you can bind function callbacks directly inside the collectionEvents object:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  collectionEvents: {
    'update': function() {
      console.log('the collection was updated');
    }
  }
})

Listening to Both

If your view has a model and collection attached, it will listen for events on both:

var Mn = require('backbone.marionette');

var MyView = Mn.View.extend({
  modelEvents: {
    'change:someattribute': 'changeMyAttribute'
  },

  collectionEvents: {
    update: 'modelsChanged'
  },

  changeMyAttribute: function() {
    console.log('someattribute was changed');
  },

  modelsChanged: function() {
    console.log('models were added or removed in the collection');
  }
})

In this case, Marionette will bind event handlers to both.

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