Question

我有一个名为CartItem的模型：

var CartItem = Backbone.Model.extend({

    // Will contain three attributes.
    // These are their default values

    defaults: {
        plucode: 0,
        title: 'cnpdx.cart',
        discount: 100,
        qty: 5,
        price: 100,
        extendcode: 0,
        checked: false,
        salemode: 1,
        comcode: 0,
        publisher: '',
        guide: '3',
        guidename: '现货'
    },

    toggle: function () {
        this.set('checked', !this.get('checked'));
    }
});

一个名为CartList的集合模型：

var CartList = Backbone.Collection.extend({

    model: CartItem,

    defaults: {
        totalFixPrice: 0,
        totalQty: 0,
        totalDiscountPrice: 0,
        totals: 0,
        checked: false
    },

    getChecked: function () {
        return this.where({checked: true});
    },

    getByComcode: function (comcode) {
        return this.where({comcode: comcode});
    }

    toggle: function () {
        this.set('checked', !this.get('checked'));
        this.model.set('checked', !this.get('checked'));
    }

});

我用一些cartitems创建了一个集合：

var cartList = new CartList([
    new CartItem({plucode:'123451', title: 'web development',discount:80,qty:5, price: 200,extendcode:'123451',salemode:1,comcode:'7-301',publisher:'北京大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode:'123452', title: 'web design', discount:80,qty:5,price: 250,extendcode:'123452',salemode:1,comcode:'7-301',publisher:'北京大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode:'123453', title: 'photography', discount:80,qty:5,price: 100,extendcode:'123451,123452',salemode:2,comcode:'7-301',publisher:'北京大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode:'123454', title: 'coffee drinking', discount:80,qty:5,price: 10,extendcode:'123451,123452',salemode:2,comcode:'7-301',publisher:'北京大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode: '123421', title: 'web development', discount: 80, qty: 5, price: 200, extendcode: '123421', salemode: 1,comcode:'7-302',publisher:'清华大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode: '123422', title: 'web design', discount: 80, qty: 5, price: 250, extendcode: '123422', salemode: 1,comcode:'7-302',publisher:'清华大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode: '123423', title: 'photography', discount: 80, qty: 5, price: 100, extendcode: '123421,123422', salemode: 2,comcode:'7-302',publisher:'清华大学出版社',guide:3,guidename:'现货'}),
    new CartItem({plucode: '123424', title: 'coffee drinking', discount: 80, qty: 5, price: 10, extendcode: '123421,123422', salemode: 2,comcode:'7-302',publisher:'清华大学出版社',guide:3,guidename:'现货'})
    // Add more here
]);

现在，我想通过'comcode'将cartList分组，所以我使用

_.groupBy(cartList, 'comcode')

但它出现错误：

Uncaught TypeError: Cannot read property 'comcode' of undefined

你能帮帮我吗？

Answer 1

您正尝试按主干集合进行分组，但是您使用_.groupBy()的方式假定您拥有一组JSON对象，而实际上并不是Backbone集合。 comcode属性是集合的模型属性的属性。 Backbone Collections和Models不会将其属性存储为Collection / Model本身的直接属性。它们存储在attributes属性中，并使用get和set函数进行访问。因此CartItem.comcode不存在且未定义。要访问模型的comcode属性，您需要执行以下操作：

var cartitem =new CartItem({plucode:'123451', title: 'web development',discount:80,qty:5, price: 200,extendcode:'123451',salemode:1,comcode:'7-301',publisher:'北京大学出版社',guide:3,guidename:'现货'})

var comcode = cartitem.get("comcode ");

因此，在您的案例中，您可以执行以下任一操作：

_.groupBy(cartList.models, function (cartitem) {
    cartitem.get("comcode ");
})

甚至更好，因为Backbone代理Underscore的groupBy函数：

cartList.groupBy(function (cartitem) {
    cartitem.get("comcode ");
})

如何使用groupBy of underscore.js通过字符串属性对Backbone.js中的集合进行分组？

1 个答案: