backbone.js1.3.3------------------------view

Posted 2020-07-26

  1 // Backbone.View
  2   // -------------
  3 
  4   // Backbone Views are almost more convention than they are actual code. A View
  5   // is simply a javascript object that represents a logical chunk of UI in the
  6   // DOM. This might be a single item, an entire list, a sidebar or panel, or
  7   // even the surrounding frame which wraps your whole app. Defining a chunk of
  8   // UI as a **View** allows you to define your DOM events declaratively, without
  9   // having to worry about render order ... and makes it easy for the view to
 10   // react to specific changes in the state of your models.
 11 
 12   // Creating a Backbone.View creates its initial element outside of the DOM,
 13   // if an existing element is not provided...
 14   //option中可以传递的参数包括
 15   //{model:模型名称,
 16   // collection:集合名称，
 17   // el：要将html模板添加到的元素，
 18   // id:el的id属性，若没有el则默认创建id为这个的div，其属性为下面的attributes，tagName，className，
 19   // attributes：
 20   // tagName：
 21   // className：
 22   // events：该元素绑定的事件}，
 23   // 在执行自定义的initialize时会将这些属性，events绑定到元素上
 24   var View = Backbone.View = function(options) {
 25     this.cid = _.uniqueId(‘view‘);
 26     this.preinitialize.apply(this, arguments);
 27     _.extend(this, _.pick(options, viewOptions));
 28     this._ensureElement();
 29     this.initialize.apply(this, arguments);
 30   };
 31 
 32   // Cached regex to split keys for `delegate`.
 33   var delegateEventSplitter = /^(\S+)\s*(.*)$/;
 34 
 35   // List of view options to be set as properties.
 36   var viewOptions = [‘model‘, ‘collection‘, ‘el‘, ‘id‘, ‘attributes‘, ‘className‘, ‘tagName‘, ‘events‘];
 37 
 38   // Set up all inheritable **Backbone.View** properties and methods.
 39   _.extend(View.prototype, Events, {
 40 
 41     // The default `tagName` of a View‘s element is `"div"`.
 42     tagName: ‘div‘,
 43 
 44     // jQuery delegate for element lookup, scoped to DOM elements within the
 45     // current view. This should be preferred to global lookups where possible.
 46     $: function(selector) {
 47       return this.$el.find(selector);
 48     },
 49 
 50     // preinitialize is an empty function by default. You can override it with a function
 51     // or object.  preinitialize will run before any instantiation logic is run in the View
 52     preinitialize: function(){},
 53 
 54     // Initialize is an empty function by default. Override it with your own
 55     // initialization logic.
 56     initialize: function(){},
 57 
 58     // **render** is the core function that your view should override, in order
 59     // to populate its element (`this.el`), with the appropriate HTML. The
 60     // convention is for **render** to always return `this`.
 61     render: function() {
 62       return this;
 63     },
 64 
 65     // Remove this view by taking the element out of the DOM, and removing any
 66     // applicable Backbone.Events listeners.
 67     remove: function() {
 68       this._removeElement();
 69       this.stopListening();
 70       return this;
 71     },
 72 
 73     // Remove this view‘s element from the document and all event listeners
 74     // attached to it. Exposed for subclasses using an alternative DOM
 75     // manipulation API.
 76     _removeElement: function() {
 77       this.$el.remove();
 78     },
 79 
 80     // Change the view‘s element (`this.el` property) and re-delegate the
 81     // view‘s events on the new element.
 82     setElement: function(element) {
 83       this.undelegateEvents();
 84       this._setElement(element);
 85       this.delegateEvents();
 86       return this;
 87     },
 88 
 89     // Creates the `this.el` and `this.$el` references for this view using the
 90     // given `el`. `el` can be a CSS selector or an HTML string, a jQuery
 91     // context or an element. Subclasses can override this to utilize an
 92     // alternative DOM manipulation API and are only required to set the
 93     // `this.el` property.
 94     _setElement: function(el) {
 95       this.$el = el instanceof Backbone.$ ? el : Backbone.$(el);
 96       this.el = this.$el[0];
 97     },
 98 
 99     // Set callbacks, where `this.events` is a hash of
100     //
101     // *{"event selector": "callback"}*
102     //
103     //     {
104     //       ‘mousedown .title‘:  ‘edit‘,
105     //       ‘click .button‘:     ‘save‘,
106     //       ‘click .open‘:       function(e) { ... }
107     //     }
108     //
109     // pairs. Callbacks will be bound to the view, with `this` set properly.
110     // Uses event delegation for efficiency.
111     // Omitting the selector binds the event to `this.el`.
112     delegateEvents: function(events) {
113       events || (events = _.result(this, ‘events‘));
114       if (!events) return this;
115       this.undelegateEvents();
116       for (var key in events) {
117         var method = events[key];
118         if (!_.isFunction(method)) method = this[method];
119         if (!method) continue;
120         var match = key.match(delegateEventSplitter);
121         this.delegate(match[1], match[2], _.bind(method, this));
122       }
123       return this;
124     },
125 
126     // Add a single event listener to the view‘s element (or a child element
127     // using `selector`). This only works for delegate-able events: not `focus`,
128     // `blur`, and not `change`, `submit`, and `reset` in Internet Explorer.
129     delegate: function(eventName, selector, listener) {
130       this.$el.on(eventName + ‘.delegateEvents‘ + this.cid, selector, listener);
131       return this;
132     },
133 
134     // Clears all callbacks previously bound to the view by `delegateEvents`.
135     // You usually don‘t need to use this, but may wish to if you have multiple
136     // Backbone views attached to the same DOM element.
137     undelegateEvents: function() {
138       if (this.$el) this.$el.off(‘.delegateEvents‘ + this.cid);
139       return this;
140     },
141 
142     // A finer-grained `undelegateEvents` for removing a single delegated event.
143     // `selector` and `listener` are both optional.
144     undelegate: function(eventName, selector, listener) {
145       this.$el.off(eventName + ‘.delegateEvents‘ + this.cid, selector, listener);
146       return this;
147     },
148 
149     // Produces a DOM element to be assigned to your view. Exposed for
150     // subclasses using an alternative DOM manipulation API.
151     _createElement: function(tagName) {
152       return document.createElement(tagName);
153     },
154 
155     // Ensure that the View has a DOM element to render into.
156     // If `this.el` is a string, pass it through `$()`, take the first
157     // matching element, and re-assign it to `el`. Otherwise, create
158     // an element from the `id`, `className` and `tagName` properties.
159     _ensureElement: function() {
160       if (!this.el) {
161         var attrs = _.extend({}, _.result(this, ‘attributes‘));
162         if (this.id) attrs.id = _.result(this, ‘id‘);
163         if (this.className) attrs[‘class‘] = _.result(this, ‘className‘);
164         this.setElement(this._createElement(_.result(this, ‘tagName‘)));
165         this._setAttributes(attrs);
166       } else {
167         this.setElement(_.result(this, ‘el‘));
168       }
169     },
170 
171     // Set attributes from a hash on this view‘s element.  Exposed for
172     // subclasses using an alternative DOM manipulation API.
173     _setAttributes: function(attributes) {
174       this.$el.attr(attributes);
175     }
176 
177   });