Mongoengine 简明教程

MongoEngine - Javascript

MongoEngine 的 QuerySet 对象具有 exec_js() 方法，该方法允许在 MongoDB 服务器上执行 Javascript 函数。此函数处理以下参数 -

QuerySet object of MongoEngine has exec_js() method that allows execution of a Javascript function on MongoDB server. This function processes the following arguments −

exec_js(code, *field_names, **options)

其中，

Where,

  1. code − a string containing Javascript code to execute

  2. fields − to be used in your function, which will be passed as arguments

  3. options − options that you want available to the function (accessed in Javascript through the options object)

此外，还可以按以下方式将一些其他变量提供给函数作用域：

In addition, some more variables are also made available to the function’s scope as given below −

  1. collection − name of the collection corresponding to the Document class. This should be used to get the Collection object from db in Javascript code.

  2. query − the query that has been generated by the QuerySet object; passed into the find() method on a Collection object in the Javascript function.

  3. options − an object containing the keyword arguments passed into exec_js().

请注意，MongoEngine 文档类中的属性在数据库中使用不同的名称（使用 Field 构造函数中的 db_field 关键字参数设置）。

Note that attributes in MongoEngine document class may use different names in the database (set using the db_field keyword argument to a Field constructor).

class BlogPost(Document):
title = StringField(db_field='doctitle')

为此，存在一种机制，可以在 Javascript 代码中将 MongoEngine 字段属性替换为数据库字段名。

For this purpose, a mechanism exists for replacing MongoEngine field attribute with the database field names in Javascript code.

当在集合对象中访问一个字段时，请使用方括号符号，并在 MongoEngine 字段名前加上一个波形符号 (~)。波形符号后的字段名将转换为在数据库中使用的名称。

When accessing a field on a collection object, use square-bracket notation, and prefix the MongoEngine field name with a tilde (~) symbol. The field name that follows the tilde will be translated to the name used in the database.

document': doc[~title];

请注意，当 Javascript 代码引用嵌入式文档中的字段时，应在嵌入式文档中的字段名之前使用嵌入式文档字段的名称，后跟一个点。

Note that when Javascript code refers to fields on embedded documents, the name of the EmbeddedDocumentField, followed by a dot, should be used before the name of the field on the embedded document.