Mongoid如何知道字符串值和符号值之间的区别？

Question

考虑这个例子:

> x = User.first # or any persisted Mongoid::Document
=> #<User _id: 52014532a6356d1ac9000001, ...>
> x.set :foo, :bar
=> :bar
> x.set :foo2, 'bar'
=> "bar"

请注意,"foo"和"foo2"未在Ruby中声明.

那么,在MongoDB shell中:

> db.users.findOne({_id: ObjectId('52014532a6356d1ac9000001')})    
{
  "_id" : ObjectId("52014532a6356d1ac9000001"),
  "foo" : "bar",
  "foo2" : "bar",
  ...
}

但现在,回到Ruby:

> x = User.find x.id; nil # to clear out any possibility of metadata on the instance
=> nil
> [x.read_attribute(:foo), x.read_attribute(:foo2)]
=> [:bar, "bar"]

怎么知道的？

Answer 1

看起来 BSON 支持值的符号类型，谷歌搜索我发现了它：

https://github.com/mongodb/mongo-ruby-driver/wiki/FAQ#FrequentlyAskedQuestions-Ruby-IseethatBSONsupportsasymboltype.DoesthismeanthatIcanstoreRubysymbolsinMongoDB%3F