Really excellent stuff Dave. I look forward to incorporating this
stuff as soon as it appears.
Thanks.
On Feb 4, 3:45 pm, David Pollak <feeder.of.the.be...@gmail.com> wrote:
> Folks,
> I'm been working on the updates to the ESME REST APIs.
>
> I've reduced the call cycle to something that looks like:
>
> 1. A request is dispatched based on the URL
> 2. The target of the dispatch returns a Box[T] where T is the type of the
> thing that will be calculated if it can be
> 1. T might be Boolean, Int, User, etc.
> 2. It's in a Box because it perhaps cannot be calculated (e.g., not
> enough permissions, etc.)
> 3. The Box can be a Failure or even a FailureParam. In the case of
> FailureParam, the param is the HTTP return code
> 3. The result is put in an IntermediateAnswer along with a function that
> can convert from T to the expected HTTP response type (e.g., XML or JSON)
> 4. The IntermediateAnswer is queried in order to build the actual
> response.
>
> With a nice dose of implicit, the code becomes very clean:
>
> val dispatch: RetType = {
> case Req("rest" :: "status" :: Nil, "", GetRequest) => status()
> case Req("rest" :: "login" :: Nil, "", PostRequest) => login()
> case Req("rest" :: "logout" :: Nil, "", GetRequest) => logout()
> case Req("rest" :: "message" :: Nil, "", GetRequest) => getMsgs()
> }
>
> And let's see some implementations:
> def status() = User.currentUser ?~ "No Session" ~> 400
>
> def logout() = {
> User.logUserOut()
> true
> }
>
> In status(), if there's no user logged in, we create a "No Session" error
> message and return a 400.
>
> In logout(), we just return true.
>
> Now, the implicit magic comes from:
> implicit def boolToResp(v: Boolean, t: RequestedResponse): LiftResponse =
> (v, t) match {
> case (v, XMLReqResponse) => new XmlResponse(<resp answer={v.toString}/>)
> case (v, JSONReqResponse) => JSONResponse(v)
> }
>
> implicit def userToResp(v: User, t: RequestedResponse): LiftResponse = (v,
> t) match {
> case (v, XMLReqResponse) => new XmlResponse(v.toXml)
> case (v, JSONReqResponse) => JSONResponse(v.asJs)
> }
>
> The code will automatically pick up these methods that convert from the
> object type to the appropriate response type. One of these "views" must
> exist for each type that is returned from a dispatched method.
>
> As I finish this stuff up, I'll roll it into some generic Lift classes.
>
> Thanks,
>
> David
>
> --
> Lift, the simply functional web frameworkhttp://liftweb.net
> Beginning Scalahttp://www.apress.com/book/view/1430219890
> Follow me:http://twitter.com/dpp
> Git some:http://github.com/dpp
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