/docs/40/50.md

 1# Type Modification
 2
 3A field may be used to generate other instances of `Field`. This can
 4be convenient to alter the type or name of a field. Since `Field` is
 5immutable, it simply generates another instance.
 6
 7## Index
 8
 9When defining indexes, MongoDB lets define ascending or descending
10order, hence the same field name is used as a key, but value is `Int`
11regardless of the original type it has. So, `Field[T]` has method
12`int` to quickly create a `Field[Int]` with the same name:
13
14```scala
15val userName = "uname".fieldOf[String]
16collection.ensureIndex(userName.int === 1, userName.int === -1)
17```
18
19## Any Field
20
21`Field[Any]` field (created by `any` method) may be helpful to write
22or read a field "as is". If you absolutely certain in what you are
23doing, 
24
25```scala
26collection.modify(userName === "john", userName.any.set(10566))
27```
28
29* * *