Node.js 在单独的模块中定义 Mongoose 模型

我想把我的mongoose 模型放在一个单独的文件里.我试图这样做:

var mongoose = require("mongoose");
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;

var Material = new Schema({
    name                :    {type: String, index: true},
    id                  :    ObjectId,
    materialId          :    String,
    surcharge           :    String,
    colors              :    {
        colorName       :    String,
        colorId         :    String,
        surcharge       :    Number
    }
});

var SeatCover = new Schema({
    ItemName            :    {type: String, index: true},
    ItemId              :    ObjectId,
    Pattern             :    String,
    Categories          :    {
        year            :    {type: Number, index: true},
        make            :    {type: String, index: true},
        model           :    {type: String, index: true},
        body            :    {type: String, index: true}
    },
    Description         :    String,
    Specifications      :    String,
    Price               :    String,
    Cost                :    String,
    Pattern             :    String,
    ImageUrl            :    String,
    Materials           :    [Materials]
});

mongoose.connect('mongodb://127.0.0.1:27017/sc');

var Materials = mongoose.model('Materials', Material);
var SeatCovers = mongoose.model('SeatCover', SeatCover);

exports.Materials = Materials;
exports.SeatCovers = SeatCovers;

然后，我try 使用这样的模型:

var models = require('./models'); 

exports.populateMaterials = function(req, res){
    console.log("populateMaterials");
    for (var i = 0; i < materials.length; i++ ){
        var mat = new models.Materials();
        console.log(mat);
        mat.name = materials[i].variantName;
        mat.materialId = materials[i].itemNumberExtension;
        mat.surcharge = materials[i].priceOffset;
        for (var j = 0; j < materials[i].colors.length; j++){
            mat.colors.colorName = materials[i].colors[j].name;
            mat.colors.colorId = materials[i].colors[j].itemNumberExtension;
            mat.colors.surcharge = materials[i].colors[j].priceOffset;
        }
        mat.save(function(err){
            if(err){
                console.log(err);
            } else {
                console.log('success');
            }
        });
    }
    res.render('index', { title: 'Express' });
};

这是在单独模块中引用模型的合理方法吗？