无法读取未定义猫鼬/ mongo的属性

Question

您可以在此链接中查看完整代码here

> function seedDB () {
Campgrounds.remove({},function(err){
    if (err) {
        console.log(err);
    }    
    else {
        console.log("Removed All Camping Sites!");
        data.forEach(function(seed){
            Campgrounds.create(seed,function(err){
                if (err) {
                    console.log(err);
                }
                else {
                    console.log("A Campground Has Been Successfully Added!");
                    Comments.create ({
                        title:"Really Great  Place, Definately worth it.",
                        author:"Chris"
                    },function(err,comment){
                        if (err) {
                            console.log(err);
                        }
                        else {
                            Campgrounds.comments.push(comment);
                            Campgrounds.save();
                            console.log("comment added");
                        }
                    });
                }
                
            });
        });
    }
});

}

一切正常，直到Campgrounds.comments.push（...）都抛出错误“无法读取未定义的类似内容。所有模块和文件都包含在我的github中。”