[英]Mongoose schema inheritance and model populate
我一直在嘗試使用mongoose的內置繼承功能(而不是擴展插件)但到目前為止還沒有太多運氣。 這是我嘗試使用的代碼的簡化示例,它表現出相同的問題。 這是基於使用鑒別器的模式繼承的mongoose文檔的擴展版本 - http://mongoosejs.com/docs/api.html#model_Model.discriminator
var util = require('util');
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/problem');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;
function BaseSchema() {
Schema.apply(this, arguments);
this.add({
name: String,
createdAt: Date
});
}
util.inherits(BaseSchema, Schema);
var BossStatusSchema = new Schema({
status: String
});
var BossStatus = mongoose.model('BossStatus', BossStatusSchema);
var PersonSchema = new BaseSchema();
var Person = mongoose.model('Person', PersonSchema);
var BossSchema = new BaseSchema({
department: String,
bossStatus: {
type: ObjectId,
ref: 'BossStatus'
}
});
var Boss = Person.discriminator('Boss', BossSchema);
添加文檔的示例代碼:
var superBoss = new BossStatus({
status: 'super'
});
var normalBoss = new BossStatus({
status: 'normal'
});
var andy = new Person({
name: 'Andy'
});
var billy = new Boss({
name: 'Billy',
bossStatus: superBoss._id
});
var callback = function(err, result) {
console.dir(err);
console.dir(result);
};
superBoss.save(callback);
normalBoss.save(callback);
andy.save(callback);
billy.save(callback);
所以當找到沒有填充的記錄時:
Person
.findOne({
name: 'Billy'
})
.exec(callback);
結果如預期的那樣,bossStatus引用了來自bossstatuses集合的_id:
null
{ name: 'Billy',
bossStatus: 52a20ab0185a7f4530000001,
_id: 52a20ab0185a7f4530000004,
__v: 0,
__t: 'Boss' }
添加填充調用時:
Person
.findOne({
name: 'Billy'
})
.populate('bossStatus')
.exec(callback);
Person結果的最終bossStatus屬性為null :
null
{ name: 'Billy',
bossStatus: null,
_id: 52a20ab0185a7f4530000004,
__v: 0,
__t: 'Boss' }
編輯:
好吧,我剛剛把可能是我想要實現的更好的例子放在一起,模式結構更適合於關系數據庫,但希望能使問題更加清晰。
var util = require('util');
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/problem');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;
function BaseSchema() {
Schema.apply(this, arguments);
this.add({
name: {
type: String,
unique: true,
required: true
}
});
}
util.inherits(BaseSchema, Schema);
var DeviceSchema = new BaseSchema();
var LocalDeviceSchema = new BaseSchema({
driver: {
type: ObjectId,
ref: 'Driver'
}
});
var RemoteDeviceSchema = new BaseSchema({
networkAddress: {
type: ObjectId,
ref: 'NetworkAddress'
}
});
var DriverSchema = new Schema({
name: {
type: String,
unique: true,
required: true
}
});
var NetworkHostSchema = new Schema({
host: {
type: String,
unique: true,
required: true
}
});
var NetworkAddressSchema = new Schema({
networkHost: {
type: ObjectId,
ref: 'NetworkHost'
},
port: {
type: Number,
min: 1,
max: 65535
}
});
var Driver = mongoose.model('Driver', DriverSchema);
var NetworkHost = mongoose.model('NetworkHost', NetworkHostSchema);
var NetworkAddress = mongoose.model('NetworkAddress', NetworkAddressSchema);
var Device = mongoose.model('Device', DeviceSchema);
var LocalDevice = Device.discriminator('LocalDevice', LocalDeviceSchema);
var RemoteDevice = Device.discriminator('RemoteDevice', RemoteDeviceSchema);
var networkHost = new NetworkHost({
host: '192.168.2.1'
});
var networkAddress = new NetworkAddress({
networkHost: networkHost._id,
port: 3000
});
var remoteDevice = new RemoteDevice({
name: 'myRemoteDevice',
networkAddress: networkAddress._id
});
var driver = new Driver({
name: 'ftdi'
});
var localDevice = new LocalDevice({
name: 'myLocalDevice',
driver: driver._id
});
var callback = function(err, result) {
if(err) {
console.log(err);
}
console.dir(result);
};
/*
// Uncomment to save documents
networkHost.save(function() {
networkAddress.save(function() {
remoteDevice.save(callback);
});
});
driver.save(function() {
localDevice.save(callback);
});
*/
var deviceCallback = function(err, device) {
if(err) {
console.log(err);
}
switch(device.__t) {
case 'LocalDevice':
console.log('Would create a local device instance passing populated result');
break;
case 'RemoteDevice':
console.log('Would create a remote device instance passing populated result');
break;
}
};
Device
.findOne({name: 'myLocalDevice'})
.populate('driver')
.exec(deviceCallback);
LocalDevice和RemoteDevice模式可能(並且可能會)包含其他差異。例如,交換機將使用DeviceFactory或其他東西來創建實例。 我的想法是應該可以通過'name'在設備表中搜索設備並填充集合引用(如果這是正確的術語?)而不必指定要搜索的集合 - 這是我對點的理解架構繼承 - 還是我完全被誤解了?
感謝您的回復!
你正在尋找一個老板,而不是一個人:
Boss
.findOne({
name: 'Billy'
})
.populate('bossStatus')
.exec(callback);
看起來像個bug。 在調試處於活動狀態時,這是針對填充查詢顯示的內容:
Mongoose: people.findOne({ name: 'Billy' }) { fields: undefined } Mongoose: people.find({ _id: { '$in': [ ObjectId("52a221ee639cc03d71000001") ] } }) { fields: undefined }
(顯示的 ObjectId
是存儲在bossStatus
的ObjectId
)
所以Mongoose正在查詢錯誤的集合( people
而不是bossstatuses
)。
正如@regretoverflow指出的那樣,如果你正在尋找老板,請使用Boss
模型而不是Person
模型。
如果您確實希望通過Person
模型填充bossStatus
,則可以顯式聲明需要搜索填充的模型:
.populate({ path : 'bossStatus', model : 'BossStatus' }) // or shorter but less clear: // .populate('bossStatus', {}, 'BossStatus')
編輯:(使用您的Device
示例)
driver
是LocalDeviceSchema
一部分,但是你要查詢Device
模型,它沒有driver
概念,並且在Device
實例的上下文中填充driver
對Mongoose沒有意義。
填充每個實例的另一種可能性是在檢索文檔后執行此操作。 你已經有了deviceCallback
功能,這可能會起作用:
var deviceCallback = function(err, device) { if(err) { console.log(err); } switch(device.__t) { // or `device.constructor.modelName` case 'LocalDevice': device.populate('driver', ...); break; case 'RemoteDevice': device.populate('networkAddress', ...); break; } };
原因是該文檔已經被轉換為正確的模型,當您使用find
populate
時,顯然不會發生這種情況。
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