Using a Box / Failure and how to set HTTP status code

[bg]

Hi all,

Three questions ->

1) Is this an appropriate way to use Box? 

2) My nested matches in userAllowed, are feeling alot like a bunch of if statements, so any more concise way to express all those checks?

3) How do I set the HTTP status of the response? I can see some examples around status but haven't been able to find exactly how I would respond with a specifc code (like a 401) for a specific condition.

val return_string = resourceAction.userAllowed("addConnection") match {

      case Full(true) => {

        UserConnectionHelper.addUserConnection(Session.currentUser.get.pk, badgeNumber)

        "this will return the JSON of the new connection to be rendered in the browser"

      }

      case Failure(msg, exception, failure) => msg

    }

    Full(JsonResponse(JString(return_string)))

}

userAllowed

//This is just checking that a bunch of criteria are met, and needs to return a specific message for the one that isn't

def userAllowed(action: String): Box[Boolean] = {

  

  action match {

      case "addConnection" => {

        Session.defaultEvent match {

          case Some(event) => event.name.get match {

            case "XYZ" => Session.currentUser match { //must be a XYZ event

              case Some(user) => { ////user must be logged in

                user.type.get match {

                  case "PQR" => Full(true) //must be logged in

                  case _ => Failure("addConnection not allowed for users of type " + user.avatar.get)

              }

              case None => Failure("addConnection only allowed for logged in users")

....

....

[David Pollak]

Please do not use pattern matching, please use for comprehensions.

Please see http://lift.la/scala-option-lift-box-and-how-to-make-your-co

Specifically, please use for comprehensions.

Also, please read http://simply.liftweb.net/index-5.3.html#toc-Section-5.3

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[Naftoli Gugenheim]

On Mon, Oct 8, 2012 at 5:49 PM, David Pollak <feeder.of...@gmail.com> wrote:

Please do not use pattern matching, please use for comprehensions.

Why? And, how do you handle the Failure case?

[Maarten Koopmans]

This returns "extracted" wrapped in a Box[SomeType] assuming that SomeValue is if Box[SomeType]:

for ( extracted <- SomeValue ?~ "param failure error message" ~> 401) yield extracted

Of course you can add processing logic in the yield using a helper function (so you get yield f(extracted))

Does this help?

--Maarten

[bg]

Hi guys,

How would I get the message in the "Failure" using a for comprehension.

In my first post - userAllowed functions does some checking, and has different messages for different scenarios?

for ( extracted <- SomeValue ?~ "param failure error message" # instead of writing this message, can I look at the Failure and get the message returned with it? # ~> 401) yield extracted

[David Pollak]

for {

  user <- User.find.filter(_.isTheRightUser) ?~ "Wrong user" ~> 407

} yield user.name

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[bg]

Sorry guys - I'm still not quite understanding what I need to. 

David - as I read your example - the error message is still being created after a Failure is returned. I would like to have "userDoes" as a helper function which checks multiple conditions, and the appropriate error can be extracted from the Failure that is returned. 

I tried the below - but get a compilation error

for {

      allowed <- resourceAction.userDoes("addConnection") ?~ _.msg ~> 407

    } yield {

      ...

missing parameter type for expanded function ((x$4) => resourceAction.userDoes("addConnection").$qmark$tilde(x$4.msg).$tilde$greater(407))

[error]       allowed <- resourceAction.userDoes("addConnection") ?~ _.msg ~> 407

[Naftoli Gugenheim]

I see now there was some miscommunication. When DPP said to use for comprehensions, he was answering question #2. So the rule of thumb is: if all your pattern match cases return a Box, you can probably unify them with for comprehensions. However in the first snippet, you need the pattern match, since the expression has to evaluate to a string. openOr won't help since you need to extract the Failure's msg.

[Naftoli Gugenheim]

On Mon, Oct 8, 2012 at 8:09 AM, bg <brent...@gmail.com> wrote:

3) How do I set the HTTP status of the response? I can see some examples around status but haven't been able to find exactly how I would respond with a specifc code (like a 401) for a specific condition.

 Full(JsonResponse(JString(return_string), 401))