Documents文档

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~~Mongoose documents represent a one-to-one mapping to documents as stored in MongoDB.~~ Mongoose文档表示存储在MongoDB中的文档的一对一映射。~~Each document is an instance of its Model.~~每个文档都是其模型的一个实例。

~~Documents vs Models~~文档与模型的对比
~~Retrieving~~检索
~~Updating Using save()~~使用save()更新
~~Updating Using Queries~~使用查询更新
~~Validating~~验证
~~Overwriting~~覆盖

Documents vs Models文档与模型的对比

~~Document and Model are distinct classes in Mongoose.~~ Document和Model是Mongoose中不同的类。~~The Model class is a subclass of the Document class.~~ Model类是Document类的一个子类。~~When you use the Model constructor, you create a new document.~~当您使用Model构造函数时，您将创建一个新文档。

const MyModel = mongoose.model('Test', new Schema({ name: String }));
const doc = new MyModel();

doc instanceof MyModel; // true
doc instanceof mongoose.Model; // true
doc instanceof mongoose.Document; // true

~~In Mongoose, a "document" generally means an instance of a model.~~ 在Mongoose中，“文档”通常意味着模型的一个实例。~~You should not have to create an instance of the Document class without going through a model.~~您不应该在不经过模型的情况下创建Document类的实例。

Retrieving检索

~~When you load documents from MongoDB using model functions like findOne(), you get a Mongoose document back.~~当您使用findOne()等模型函数从MongoDB加载文档时，您会得到一个Mongoose文档。

const doc = await MyModel.findOne();

doc instanceof MyModel; // true
doc instanceof mongoose.Model; // true
doc instanceof mongoose.Document; // true

Updating Using `save()`使用`save()`更新

~~Mongoose documents track changes.~~ Mongoose文档跟踪更改。~~You can modify a document using vanilla JavaScript assignments and Mongoose will convert it into MongoDB update operators.~~您可以使用普通的JavaScript赋值修改文档，Mongoose会将其转换为MongoDB更新运算符。

doc.name = 'foo';

// Mongoose sends an `updateOne({ _id: doc._id }, { $set: { name: 'foo' } })` to MongoDB.Mongoose向MongoDB发送了一个`updateOne({ _id: doc._id }, { $set: { name: 'foo' } })`
await doc.save();

~~The save() method returns a promise.~~ save()方法返回一个promise。~~If save() succeeds, the promise resolves to the document that was saved.~~如果save()成功，promise将解析为已保存的文档。

doc.save().then(savedDoc => {
  savedDoc === doc; // true
});

~~If the document with the corresponding _id is not found, Mongoose will report a DocumentNotFoundError:~~如果找不到具有相应_id的文档，Mongoose将报告DocumentNotFoundError：

const doc = await MyModel.findOne();

// Delete the document so Mongoose won't be able to save changes删除文档，使Mongoose无法保存更改
await MyModel.deleteOne({ _id: doc._id });

doc.name = 'foo';
await doc.save(); // Throws 抛出DocumentNotFoundError

Updating Using Queries使用查询更新

~~The save() function is generally the right way to update a document with Mongoose.~~ save()函数通常是用Mongoose更新文档的正确方法。~~With save(), you get full validation and middleware.~~使用save()，您可以获得完整的验证和中间件。

~~For cases when save() isn't flexible enough, Mongoose lets you create your own MongoDB updates with casting, middleware, and limited validation.~~对于save()不够灵活的情况，Mongoose允许您使用强制转换、中间件和有限的验证来创建自己的MongoDB更新。

// Update all documents in the `mymodels` collection
await MyModel.updateMany({}, { $set: { name: 'foo' } });

~~Note that update(), updateMany(), findOneAndUpdate(), etc.~~ 请注意update()、updateMany()、findOneAndUpdate()等。~~do not execute save() middleware. If you need save middleware and full validation, first query for the document and then save() it.~~不要执行save()中间件。如果您需要保存中间件和完整验证，请先查询文档，然后save()它。

Validating验证

~~Documents are casted and validated before they are saved.~~ 在保存文档之前，对文档进行铸造和验证。~~Mongoose first casts values to the specified type and then validates them.~~ Mongoose首先将值强制转换为指定的类型，然后验证它们。~~Internally, Mongoose calls the document's validate() method before saving.~~在内部，Mongoose在保存之前调用文档的validate()方法。

const schema = new Schema({ name: String, age: { type: Number, min: 0 } });
const Person = mongoose.model('Person', schema);

const p = new Person({ name: 'foo', age: 'bar' });
// Cast to Number failed for value "bar" at path "age"
await p.validate();

const p2 = new Person({ name: 'foo', age: -1 });
// Path `age` (-1) is less than minimum allowed value (0).
await p2.validate();

~~Mongoose also supports limited validation on updates using the runValidators option.~~ Mongoose还支持使用runValidators选项对更新进行有限验证。~~Mongoose casts parameters to query functions like findOne(), updateOne() by default.~~ 默认情况下，Mongoose将参数强制转换为查询函数，如findOne()、updateOne()。~~However, Mongoose does not run validation on query function parameters by default. You need to set runValidators: true for Mongoose to validate.~~然而，Mongoose默认情况下不会对查询函数参数进行验证。您需要设置runValidators: true，以便Mongoose进行验证。

// Cast to number failed for value "bar" at path "age"
await Person.updateOne({}, { age: 'bar' });

// Path `age` (-1) is less than minimum allowed value (0).
await Person.updateOne({}, { age: -1 }, { runValidators: true });

~~Read the validation guide for more details.~~有关更多详细信息，请阅读验证指南。

Overwriting覆盖

~~There are 2 different ways to overwrite a document (replacing all keys in the document).~~ 覆盖文档有两种不同的方法（替换文档中的所有键）。~~One way is to use the Document#overwrite() function followed by save().~~一种方法是使用Document#overwrite()函数，然后使用save()。

const doc = await Person.findOne({ _id });

// Sets `name` and unsets all other properties设置`name`并取消设置所有其他属性
doc.overwrite({ name: 'Jean-Luc Picard' });
await doc.save();

~~The other way is to use Model.replaceOne().~~另一种方法是使用Model.replaceOne()。

// Sets `name` and unsets all other properties设置`name`并取消设置所有其他属性
await Person.replaceOne({ _id }, { name: 'Jean-Luc Picard' });

Next Up下一步

~~Now that we've covered Documents, let's take a look at Subdocuments.~~现在我们已经介绍了文档，让我们来看一下子文档。