Mongoose - 使用时不填充记录，否则为记录数组答案

【问题标题】：Mongoose - when use populate no records otherwise array of recordsMongoose - 使用时不填充记录，否则为记录数组
【发布时间】：2015-10-18 17:24:38
【问题描述】：

我正在学习 MeanJS，但我对 Mongoose 有疑问。我有两个模型：

var CategorySchema = new Schema({
    name: {
        type: String,
        default: '',
        required: 'Please fill Category name',
        trim: true
    },
    slug: {
        type: String,
        default: '',
        trim: true,
        unique: true
    },
    created: {
        type: Date,
        default: Date.now
    },
    user: {
        type: Schema.ObjectId,
        ref: 'User'
    },
    articles: [{
        type: Schema.ObjectId,
        ref: 'Article'
    }]
});

var ArticleSchema = new Schema({
    created: {
        type: Date,
        default: Date.now
    },
    category: {
        type: Schema.ObjectId,
        ref: 'Category'
    },
    title: {
        type: String,
        default: '',
        trim: true,
        required: 'Title cannot be blank'
    },
    slug: {
        type: String,
        default: '',
        trim: true,
        unique: true
    },
    content: {
        type: String,
        default: '',
        trim: true
    },
    user: {
        type: Schema.ObjectId,
        ref: 'User'
    }
});

我正在保存这样的文章：

exports.create = function(req, res) {
    var article = new Article(req.body);
    article.user = req.user;

    article.save(function(err) {
        if (err) {
            return res.status(400).send({
                message: errorHandler.getErrorMessage(err)
            });
        } else {
            Category.findById(article.category).exec(function(err, category) {
                category.articles.push(article.category);
                category.save(function(err, category) {
                    if (err) {
                        return res.status(400).send({
                            message: errorHandler.getErrorMessage(err)
                        });
                    } else {
                        res.json(article);
                    }
                });
            });

        }
    });
};

它正在正确保存。对象如下所示：

{
    "_id" : ObjectId("55b73bf97aa70c2c083655b0"),
    "user" : ObjectId("55b115f35c7a03cc0e59d821"),
    "articles" : [ 
        ObjectId("55b73c017aa70c2c083655b2"), 
        ObjectId("55b73ee20bab5e8c0c7eadca")
    ],
    "created" : ISODate("2015-07-28T08:23:21.562Z"),
    "slug" : "motocycles",
    "name" : "Motocycles",
    "__v" : 2
}

甚至当我计算像 {{ category.articles.length }} 这样的记录时，类别中的文章数量也很合适，我什至可以在视图中打印 ObjectIds。但是当我像这样添加 .populate('articles') 时：

exports.list = function(req, res) {
    Category.find().sort('-created').populate('user', 'displayName').populate('articles').exec(function(err, categories) {
        if (err) {
            return res.status(400).send({
                message: errorHandler.getErrorMessage(err)
            });
        } else {
            res.jsonp(categories);
        }
    });
};

长度返回 0，ObjectIds 消失，我无法访问文章属性，就像类别中没有文章一样。任何想法为什么会发生这种情况？

补充编辑：

mongoose.model('Article', ArticleSchema);
mongoose.model('Category', CategorySchema);

【问题讨论】：

您能否发布基于这些模式声明模型对象的行？

标签： javascript mongodb mongoose mongodb-query mongoose-populate

【解决方案1】：

First, some changes with regard to variables,schema instances and using ObjectId(The mongoose documentation isn't the best).

var categorySchema = new mongoose.Schema({
    name: {
        type: String,
        required: 'Please fill Category name',
        trim: true
    },
    slug: {
        type: String,
        trim: true,
        unique: true
    },
    created: {
        type: Date,
        default: Date.now
    },
    user: {
        type: mongoose.Types.Schema.ObjectId,
        ref: 'User'
    },
    articles: [{
        type: mongoose.Types.Schema.ObjectId,
        ref: 'Article'
    }]
});

var articleSchema = new mongoose.Schema({
    created: {
        type: Date,
        default: Date.now
    },
    category: {
        type: mongoose.Types.Schema.ObjectId,
        ref: 'Category'
    },
    title: {
        type: String,
        trim: true,
        required: 'Title cannot be blank'
    },
    slug: {
        type: String,
        trim: true,
        unique: true
    },
    content: {
        type: String,
        trim: true
    },
    user: {
        type: mongoose.Types.Schema.ObjectId,
        ref: 'User'
    }
});

You need to export your models if you are using an MV* pattern with separate files for separate concerns. So...

exports.method = mongoose.model('Category',categorySchema);
exports.otherMethod = mongoose.model('Article',articleSchema);

. method and .otherMethod are from nodejs. Not sure about express equivalent or what express itself uses.

Then just name this file and require it using its path.

【讨论】：

【解决方案2】：

似乎问题出在创建函数上。我改变了一些东西，它开始工作了：

exports.create = function(req, res) {
  var article = new Article(req.body);
  article.user = req.user;

  article.save(function(err, savedArticle) {
    if (err) {
      return res.status(400).send({
        message: errorHandler.getErrorMessage(err)
      });
    } else {
      Category.findById(article.category).exec(function (err, category) {
        category.articles.push(savedArticle);
        category.markModified('articles');

        category.save(function (err, category) {
          if (err) {
            return res.status(400).send({
              message: errorHandler.getErrorMessage(err)
            });
          } else {
            res.json(savedArticle);
          }
        });
      });
    }
  });
};

我很好奇为什么即使 Category 对象具有正确的 Article ObjectId，它也不起作用。

【讨论】：