Mongoose - 使用鉴别器划分子文档

Question

如果我有一个模型Attachment，可以分为4种类型：Link、YoutubeVideo、GoogleDriveFile和GoogleDriveFolder，如何使用Mongoose将Attachment区分为这些类型，并允许它们成为另一个模式中的子文档； Post?

我创建了基础Attachment 模型，并使用鉴别器将其划分为单独的模型：

var AttachmentSchema = new Schema({
    id:     {type: String, required: true},
    title:  {type: String, required: true}
});

var Attachment = mongoose.model('Material', AttachmentSchema);

module.exports = {
    DriveFile:      Attachment.discriminator('GoogleDriveFile', new mongoose.Schema()),
    DriveFolder:    Attachment.discriminator('GoogleDriveFolder', new mongoose.Schema()),
    Link:           Attachment.discriminator('Link', new mongoose.Schema()),
    YoutubeVideo:   Attachment.discriminator('YoutubeVideo', new mongoose.Schema())
};

现在，在Post 架构中，应该有一个附件数组，具有不同的类型：

var Attachment = require('./attachment');

var PostSchema = new Schema(
    text:{type: String},
    attachments: [Material] // Could be Material.Link, Material.YoutubeVideo, etc
});

执行此操作时，我收到一条错误消息，提示“GoogleDriveFile 处的未定义类型 Model。您是否尝试嵌套架构？您只能使用引用或数组进行嵌套。”

我不知道这个错误是什么意思，也找不到任何解释如何执行此操作的文档。帮忙？

Answer 1

尝试执行以下操作：

    var AttachmentSchema = new Schema({
    id:     {type: String, required: true},
    title:  {type: String, required: true}
    });

var PostSchema = new Schema({
    text: { type: String },
    attachments: [ AttachmentSchema ] // Could be Material.Link, Material.YoutubeVideo, etc
});

var attachmentArray = PostSchema.path('attachments');

    module.exports = {
    Post: mongoose.model('Post', PostSchema),
    DriveFile:      attachmentArray.discriminator('GoogleDriveFile', new mongoose.Schema({})),
    DriveFolder:    attachmentArray.discriminator('GoogleDriveFolder', new mongoose.Schema({})),
    Link:           attachmentArray.discriminator('Link', new mongoose.Schema({})),
    YoutubeVideo:   attachmentArray.discriminator('YoutubeVideo', new mongoose.Schema({}))
};

关键是不要使用猫鼬模型，使用父文档模式的 schema.path 作为鉴别器的基础。

在此链接上搜索术语 docArray：Mongoose Discriminator documentation