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Advanced CollectionView Usage

CollectionView provides a lot of possibilities to sort, filter and manages children.

Documentation Index

CollectionView's children

The CollectionView can store and manage its child views. This allows you to easily access the views within the collection view, iterate them, find them by a given indexer such as the view's model or collection, and more.

CollectionView's buildChildView

The buildChildView is responsible for taking the ChildView class and instantiating it with the appropriate data. This method takes three parameters and returns a view instance to be used as thechild view.

buildChildView: function(child, ChildViewClass, childViewOptions){
  // build the final list of options for the childView class
  var options = _.extend({model: child}, childViewOptions);
  // create the child view instance
  var view = new ChildViewClass(options);
  // return it
  return view;
},

Override this method when you need a more complicated build, but use childView if you need to determine which View class to instantiate.

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

var MyCollectionView = Mn.CollectionView.extend({
  childView: function(child) {
    if (child.get('type') === 'list') {
      return MyListView;
    }

    return MyView;
  },
  buildChildView: function(child, ChildViewClass, childViewOptions) {
    var options = {};

    if (child.get('type') === 'list') {
      var childList = new Bb.Collection(child.get('list'));
      options = _.extend({collection: childList}, childViewOptions);
    } else {
      options = _.extend({model: child}, childViewOptions);
    }

    // create the child view instance
    var view = new ChildViewClass(options);
    // return it
    return view;
  }

});

CollectionView's addChildView

The addChildView method can be used to add a view that is independent of your Backbone.Collection. Note that this added view will be subject to filtering and ordering and may be difficult to manage in complex situations. Use with care.

This method takes two parameters, the child view instance and the index for where it should be placed within the CollectionView's children.

var Mn = require('backbone.marionette');
var buttonView = new ButtonView();
var MyCollectionView = Mn.CollectionView.extend({
  onRender: function() {
    this.addChildView(buttonView, this.collection.length);
  }
});

var myCollectionView = new MyCollectionView();

myCollectionView.render();

CollectionView: Retrieve Child Views

You can retrieve a view by any of the index. If the findBy* method cannot find the view, it will return undefined.

CollectionView childView's: findByCid

Find a view by it's cid.

var bView = myCollectionView.children.findByCid(buttonView.cid);

CollectionView childView's: findByModel

Find a view by model.

var bView = myCollectionView.children.findByModel(buttonView.model);

CollectionView childView's: findByModelCid

Find a view by model cid.

var bView = myCollectionView.children.findByModelCid(buttonView.model.cid);

CollectionView childView's: findByCustom

Find by custom key.

var bView = myCollectionView.children.findByCustom('custom_key');

CollectionView childView's: findByIndex

Find by numeric index (unstable)

var bView = myCollectionView.children.findByIndex(0);

CollectionView's removeChildView

The removeChildView method is useful if you need to remove a view from the CollectionView without affecting the view's collection. In most cases it is better to use the data to determine what the CollectionView should display.

This method the child view instance to remove as its parameter.

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

Mn.CollectionView.extend({
  onChildViewClose: function(childView, model) {
    // NOTE: we must wait for the server to confirm
    // the destroy PRIOR to removing it from the collection
    model.destroy({wait: true});

    // but go ahead and remove it visually
    this.removeChildView(childView);
  }
});

CollectionView childView Iterators And Collection Functions

The container object borrows several functions from Underscore.js, to provide iterators and other collection functions, including:

These methods can be called directly on the container, to iterate and process the views held by the container.

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

var collectionView = new Mn.CollectionView({
  collection: new Bb.Collection()
});

collectionView.render();

// iterate over all of the views and process them
collectionView.children.each(function(childView) {
  // process the `childView` here
});

CollectionView's filter

CollectionView allows for a custom filter option if you want to prevent some of the underlying collection's models from being rendered as child views. The filter function takes a model from the collection and returns a truthy value if the child should be rendered, and a falsey value if it should not.

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

var cv = new Mn.CollectionView({
  childView: SomeChildView,
  emptyView: SomeEmptyView,
  collection: new Bb.Collection([
    { value: 1 },
    { value: 2 },
    { value: 3 },
    { value: 4 }
  ]),

  // Only show views with even values
  filter: function (child, index, collection) {
    return child.get('value') % 2 === 0;
  }
});

// renders the views with values '2' and '4'
cv.render();

// change the filter
// renders the views with values '1' and '3'
cv.setFilter(function (child, index, collection) {
  return child.get('value') % 2 !== 0;
});

// renders all views
cv.removeFilter();

CollectionView's setFilter

The setFilter method modifies the CollectionView's filter attribute, and renders the new ChildViews in a efficient way, instead of rendering the whole DOM structure again. Passing { preventRender: true } in the options argument will prevent the view being rendered.

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

var cv = new Mn.CollectionView({
  collection: someCollection
});

cv.render();

var newFilter = function(child, index, collection) {
  return child.get('value') % 2 === 0;
};

// Note: the setFilter is preventing the automatic re-render
cv.setFilter(newFilter, { preventRender: true });

//Render the new state of the ChildViews instead of the whole DOM.
cv.render();

CollectionView's removeFilter

This function is actually an alias of setFilter(null, options). It is useful for removing filters. removeFilter also accepts preventRender as a option.

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

var cv = new Mn.CollectionView({
  collection: someCollection
});

cv.render();

cv.setFilter(function(child, index, collection) {
  return child.get('value') % 2 === 0;
});

//Remove the current filter without rendering again.
cv.removeFilter({ preventRender: true });

CollectionView's sort

By default the CollectionView will maintain a sorted collection's order in the DOM. This behavior can be disabled by specifying {sort: false} on initialize. The sort flag cannot be changed after instantiation.

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

var myCollection = new Bb.Collection([
  { id: 1 },
  { id: 4 },
  { id: 3 },
  { id: 2 }
]);

myCollection.comparator = 'id';

var mySortedColView = new Mn.CollectionView({
  //...
  collection: myCollection
});

var myUnsortedColView = new Mn.CollectionView({
  //...
  collection: myCollection,
  sort: false
});

mySortedColView.render(); // 1 4 3 2
myUnsortedColView.render(); // 1 4 3 2

// mySortedColView auto-renders 1 2 3 4
// myUnsortedColView has no change
myCollection.sort();

CollectionView's viewComparator

CollectionView allows for a custom viewComparator option if you want your CollectionView's children to be rendered with a different sort order than the underlying Backbone collection uses.

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

var cv = new Mn.CollectionView({
  collection: someCollection,
  viewComparator: 'otherFieldToSortOn'
});

The viewComparator can take any of the acceptable Backbone.Collection comparator formats -- a sortBy (pass a function that takes a single argument), as a sort (pass a comparator function that expects two arguments), or as a string indicating the attribute to sort by.

CollectionView's getViewComparator

Override this method to determine which viewComparator to use.

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

var MyCollectionView = Mn.CollectionView.extend({
  sortAsc: function(model) {
    return -model.get('order');
  },
  sortDesc: function(model) {
    return model.get('order');
  },
  getViewComparator: function() {
    // The collectionView's model
    if (this.model.get('sorted') === 'ASC') {
      return this.sortAsc;
    }

    return this.sortDesc;
  }
});

CollectionView's reorderOnSort

This option is useful when you have performance issues when you resort your CollectionView. Without this option, your CollectionView will be completely re-rendered, which can be costly if you have a large number of elements or if your ChildViews are complex. If this option is activated, when you sort your Collection, there will be no re-rendering, only the DOM nodes will be reordered. This can be a problem if your ChildViews use their collection's index in their rendering. In this case, you cannot use this option as you need to re-render each ChildView.

If you combine this option with a filter that changes the views that are to be displayed, reorderOnSort will be bypassed to render new children and remove those that are rejected by the filter.

CollectionView's reorder

If reorderOnSort is set to true, this function will be used instead of re-rendering all children. It can be called directly to prevent the collection from being completely re-rendered. This may only be useful if models are added or removed silently or if sort was set to false on the CollectionView.

CollectionView's resortView

By default the CollectionView will maintain the order of its collection in the DOM. However on occasions the view may need to re-render to make this possible, for example if you were to change the comparator on the collection. The CollectionView will re-render its children or reorder them depending on reorderOnSort. Override this function if you need further customization.

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

var MyCollectionView = Mn.CollectionView.extend({
  resortView: function() {
    // provide custom logic for rendering after sorting the collection
  }
});
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