Question

I’m trying to add a new virtual field to my backbone model whenever a new item is added, the code is simple:

window.DealModel = Backbone.Model.extend({
    defaults: {
        title: '',
        desc: '',
        location: '',
        terms: '',
        price_orignial: 0,
        price_discounted: 0
    }
});

window.DealCollection = Backbone.Collection.extend({
    model: DealModel,

    initialize: function (models, options) {
        this.bind('add', this.addTitleShort);
    },

    addTitleShort: function(rdeal){
        rdeal.set('title_short', _.str.prune( rdeal.get('title') , 140, '+++'));
    }

});

However, I keep getting a _ Cannot use 'in' operator to search for 'id' in title_short_, not sure what the problem is, appreciate the help.

Answer 1

I think that “set” uses object hash:

rdeal.set( { title_short: _.str.prune( rdeal.get('title') , 140, '+++') });

But if there was no “title_short” property in the created model, I don’t know if you can “set” it. You can just do

 rdeal.title_short = _.str.prune( rdeal.get('title') , 140, '+++');

Also you can add a function to Model class that will return the result thus eliminating the need to handle model’s “change” event:

window.DealModel = Backbone.Model.extend({
    ...
    title_short: function() {
        return _.str.prune( this.get('title') , 140, '+++');
    }
});

and use it: myModelInstance.title_short();

Hope it helped.