backbone.js - accessing a model from a click event

问题:

I have a BoardView containing a CellCollection of CellModels. I fetch the collection from the db and then create the CellViews.

This all works swimmingly until I try to access a CellModel via a click event on the BoardView. I can't get to the underlying models at all... only the views. Is there a way to do this?

I've attempted to include the relevant code below:

CellModel = Backbone.Model.extend({});

CellCollection = Backbone.Collection.extend({
    model : CellModel
});

CellView = Backbone.View.extend({
    className : 'cell',
});

BoardView = Backbone.View.extend({
    this.model.cells = new CellCollection();

    render : function() {
        this.cellList    = this.$('.cells');
        return this;
    },

    allCells : function(cells) {
        this.cellList.html('');
        this.model.cells.each(this.addCell);
        return this;
    },

    addCell : function(cell) {
        var view = new Views.CellView({
            model : cell
        }).render();

        this.cellList.append(view.el);
    },

    events : {
        'click .cell' : 'analyzeCellClick',
    },

    analyzeCellClick : function(e) {
        // ?????????
    }
});

I need the click to "happen" on the BoardView, not the CellView, because it involves board-specific logic.

回答1:

I can think of at least two approaches you might use here:

1. Pass the BoardView to the CellView at initialization, and then handle the event in the CellView:

   var CellView = Backbone.View.extend({
       className : 'cell',
   
       initialize: function(opts) {
           this.parent = opts.parent
       },
   
       events : {
           'click' : 'analyzeCellClick',
       },
   
       analyzeCellClick : function() {
           // pass the relevant CellModel to the BoardView
           this.parent.analyzeCellClick(this.model);
       }
   });
   
   var BoardView = Backbone.View.extend({
       // ...
   
       addCell : function(cell) {
           var view = new Views.CellView({
               model : cell,
               parent : this
           }).render();
   
           this.cellList.append(view.el);
       },
   
       analyzeCellClick : function(cell) {
           // do something with cell
       }
   });
   

   This would work, but I prefer to not have views call each other's methods, as it makes them more tightly coupled.

2. Attach the CellModel id to the DOM when you render it:

   var CellView = Backbone.View.extend({
       className : 'cell',
   
       render: function() {
           $(this.el).data('cellId', this.model.id)
           // I assume you're doing other render stuff here as well
       }
   });
   
   var BoardView = Backbone.View.extend({
       // ...
   
       analyzeCellClick : function(evt) {
           var cellId = $(evt.target).data('cellId'),
               cell = this.model.cells.get(cellId);
           // do something with cell
       }
   });
   

   This is probably a little cleaner, in that it avoids the tight coupling mentioned above, but I think either way would work.

回答2:

Good question! I think the best solution would be to implement an

EventBus aka EventDispatcher

to coordinate all events among the different areas of your application.

Going that route seems clean, loosely coupled, easy to implement, extendable and it is actually suggested by the backbone documentation, see Backbone Docs

Please also read more on the topic here and here because (even though I tried hard) my own explanation seems kind of mediocre to me.

Five step explanation:

1. Create an EventBus in your main or somewhere else as a util and include/require it

    var dispatcher = _.clone(Backbone.Events); // or _.extends 
   

2. Add one or more callback hanlder(s) to it

    dispatcher.CELL_CLICK = 'cellClicked'
   

3. Add a trigger to the Eventlistener of your childView (here: the CellView)

    dispatcher.trigger(dispatcher.CELL_CLICK , this.model);
   

4. Add a Listener to the Initialize function of your parentView (here: the BoardView)

    eventBus.on(eventBus.CARD_CLICK, this.cardClick);
   

5. Define the corresponding Callback within of your parentView (and add it to your _.bindAll)

    cellClicked: function(model) {
    // do what you want with your data here
    console.log(model.get('someFnOrAttribute')
    }
   

回答3:

I would let the CellView handle the click event, but it will just trigger a Backbone event:

var CellView = Backbone.View.extend({
    className : 'cell',

    initialize: function() {
        _.bindAll(this, 'analyzeCellClick');
    }

    events : {
        'click' : 'analyzeCellClick',
    },

    analyzeCellClick : function() {
        this.trigger('cellClicked', this.model);
    }
});

var BoardView = Backbone.View.extend({
    // ...

    addCell : function(cell) {
        var view = new Views.CellView({
            model : cell
        }).render();

        this.cellList.append(view.el);
        view.bind('cellClicked', function(cell) {
              this.analyzeCellClick(cell);
            };
    },

    analyzeCellClick : function(cell) {
        // do something with cell
    }
});