据国外">媒体报道，Foursquare今天在GitHub上发布了两个应用程序的代码，一个是用Scala编写的MongoDB查询指定域语言Rogue，另一个是“iOS缓存图像加载器” Full-Loaded。根据Github上的说明，Rogue对于在Lift 网络框架中使用MongoDB的开发人员将非常有用；这样的开发人员目前仍然较少，但在人数却在持续增长。
Rogue is a type-safe internal Scala DSL for constructing and executing find and modify commands against MongoDB in the Lift web framework. It is fully expressive with respect to the basic options provided by MongoDB's native query language, but in a type-safe manner, building on the record types specified in your Lift models. An example:
Venue where (_.mayor eqs 1234) and (_.categories contains "Thai") fetch(10)
The type system enforces the following constraints:
·the fields must actually belong to the record (e.g., mayor is a field on the Venue record)
·the field type must match the operand type (e.g., mayor is an IntField)
·the operator must make sense for the field type (e.g., categories is a MongoListField[String])
In addition, the type system ensures that certain builder methods are only used in certain circumstances. For example, take this more complex query:
Venue where (_.closed eqs false) orderAsc(_.popularity) limit(10) modify (_.closed setTo true) updateMulti
This query purportedly finds the 10 least popular open venues and closes them. However, MongoDB does not (currently) allow you to specify limits on modify queries, so Rogue won't let you either. The above will generate a compiler error.
Constructions like this:
def myMayorships = Venue where (_.mayor eqs 1234) limit(5)
...
myMayorships.fetch(10)
will also not compile, here because a limit is being specified twice. Other similar constraints are in place to prevent you from accidentally doing things you don't want to do anyway.
More Examples
QueryTest.scala contains sample Records and examples of every kind of query supported by Rogue. It also indicates what each query translates to in MongoDB's JSON query language. It's a good place to look when getting started using Rogue.
NB: The examples in QueryTest only construct query objects; none are actually executed. Once you have a query object, the following operations are supported (listed here because they are not demonstrated in QueryTest):
For "find" query objects
val query = Venue where (_.venuename eqs "Starbucks")
query.count()
query.countDistinct(_.mayor)
query.fetch()
query.fetch(n)
query.get() // equivalent to query.fetch(1).headOption
query.foreach{v: Venue => ... }
query.paginate(pageSize)
query.fetchBatch(pageSize){vs: List[Venue] => ...}
query.bulkDelete_!!
For "modify" query objects
val modify = query modify (_.popularity inc 1)
modify.updateMulti()
modify.updateOne()
modify.upsertOne()
更多的Foursquare源代码可查看https://github.com/foursquare/