David,
I'm using your new ManyToMany trait and ran across this error:
Message: java.lang.ClassCastException: net.liftweb.mapper.ProtoUser$id
$ cannot be cast to java.lang.Long
scala.runtime.BoxesRunTime.unboxToLong(Unknown Source)
net.liftweb.mapper.MappedLong.real_i_set_$bang(MappedLong.scala:223)
net.liftweb.mapper.MappedField$class.i_set_$bang(MappedField.scala:
449)
net.liftweb.mapper.MappedLong.i_set_$bang(MappedLong.scala:223)
net.liftweb.mapper.MappedField$class.set(MappedField.scala:429)
net.liftweb.mapper.MappedLong.set(MappedLong.scala:223)
net.liftweb.mapper.ManyToMany$MappedManyToMany.own(ManyToMany.scala:
78)
My code that generates the error is:
entity.roles += r
where entity is a User and roles is the MappedManyToMany object in
User.
Glenn...
On Aug 8, 10:35 pm, Naftoli Gugenheim <[email protected]> wrote:
> Thanks, David.
> Glenn, as far as the issue of adding unsaved children, I was thinking about
> it. If the same Role can be referenced by multiple users, why are you
> creating Roles at the same time that you are adding them to a User? Shouldn't
> there be one screen to manage Roles and the User screen would only allow you
> to add existing Roles?
>
> -------------------------------------
>
> David Pollak<[email protected]> wrote:
>
> There are dependent types that mirror the parameterized types for Mapper,
> KeyedMapper, etc.
> I've updated ManyToMany to use the dependent types... it should eliminate
> the need to have the type parameters. If it breaks thing, please revert the
> changes.
>
> On Thu, Aug 6, 2009 at 9:55 AM, Naftoli Gugenheim <[email protected]>wrote:
>
> > In your use case it can only be Long and User. But there has to be a type
> > parameter because other people might have a String key and a Request mapper.
> > And the contents of ManyToMany have to be type safe to enforce their
> > consistency with however the user of ManyToMany wants them to use it. So I
> > think what you want is that the compiler should figure out that since you're
> > using it with a KeyedMapper[Long, User], which is ManyToMany's T <:
> > KeyedMapper[K,T], and ManyToMany extends KeyedMapper[K,T] and it has a self
> > type of T, and therefore it would be a compiler error to write anything
> > besides Long and User, therefore you must want to use Long and User and they
> > should be inferred.
> > I could certainly hear that, although I'm not much of a type theorist. So
> > feel free to open an enhancement ticket on Scala's Trac! :)
> > If I understood correctly...
>
> > On Thu, Aug 6, 2009 at 12:43 PM, glenn <[email protected]> wrote:
>
> >> Naftoli,
>
> >> As I said at the outset, this is really beyond my expertise. But I
> >> think it's too
> >> broad and maybe, even unnecessary. In my example, K can only be one
> >> type,
> >> Long, and T can only be of type User. Anything else, and the compiler
> >> can't be
> >> guaranteed to catch it, but try running the application and you get
> >> things like
> >> stack overflow errors.
>
> >> How you would fix this is beyond me. All you can really do, at this
> >> point, is
> >> make sure to include these kinds of restrictions in the docs.
>
> >> Glenn...
>
> >> On Aug 6, 9:33 am, Naftoli Gugenheim <[email protected]> wrote:
> >> > It's too broad, or it's too restrictive/unnecessary? I'm confused, you
> >> seem
> >> > to imply both.If it's too broad, tell me why. But if you want to know
> >> why it
> >> > needs the type parameter, it's because it has to use the type parameter
> >> in
> >> > its implentation -- just count how many times its source code uses it!
> >> And
> >> > if you want to know why the compiler can't infer it or be told to infer
> >> > it... that's another issue.
> >> > But if passing a type that creates a conflicting inheritance causes a
> >> > compiler crash, that's not something I can help. :)
> >> > Regards.
>
> >> > On Thu, Aug 6, 2009 at 12:26 PM, glenn <[email protected]> wrote:
>
> >> > > Naftoli,
>
> >> > > At the risk of discussing something obviously beyond my pay grade,
> >> > > isn't the real issue Scala traits
> >> > > and the use of parameterized types. The ManyToMany trait is defined
> >> > > as:
>
> >> > > trait ManyToMany[K,T<:KeyedMapper[K, T]]....
>
> >> > > But this isn't really correct,is it, the parameter is too broad, and
> >> > > that leads to a lot of the confusion and results in the need for
> >> > > unnecessary documentation. When you think about it, why all the
> >> > > duplication? Why do I need to
> >> > > write my User entity as:
>
> >> > > class User extends MegaProtoUser[User] with ManyToMany[Long,User]
>
> >> > > when we all know that this would be much cleaner:
>
> >> > > class User extends MegaProtoUser[User] with ManyToMany.
>
> >> > > But traits aren't like interfaces. They have implementation and would
> >> > > need to know something about
> >> > > the parent class they are attached to - and how would you accomplish
> >> > > that (reflection, maybe). This is
> >> > > more a Scala issue than a Lift one, I think.
>
> >> > > Glenn...
>
> >> > > On Aug 5, 8:24 pm, Naftoli Gugenheim <[email protected]> wrote:
> >> > > > Building causes a stack overflow?
> >> > > > So the question is, is it the resident compiler or plain scalac also
> >> > > crashes? Or just the presentation compiler? What do you see in the
> >> error log
> >> > > view or file?
> >> > > > I get compiler crashes very often when doing fancy mapper type
> >> related
> >> > > tricks.
>
> >> > > > -------------------------------------
>
> >> > > > glenn<[email protected]> wrote:
>
> >> > > > Naftoli,
>
> >> > > > Hate to do this to you, but I'm getting the following error using
> >> > > > ManyToMany for Users to Roles:
>
> >> > > > Message: java.lang.RuntimeException: Broken join
> >> > > > scala.Predef$.error(Predef.scala:76)
>
> >> > > net.liftweb.mapper.ManyToMany$MappedManyToMany$$anonfun$children$1$
> >> > > > $anonfun$apply$1.apply(ManyToMany.scala:54)
>
> >> > > net.liftweb.mapper.ManyToMany$MappedManyToMany$$anonfun$children$1$
> >> > > > $anonfun$apply$1.apply(ManyToMany.scala:54)
> >> > > > net.liftweb.util.EmptyBox.openOr(Box.scala:372)
>
> >> net.liftweb.mapper.ManyToMany$MappedManyToMany$$anonfun$children
> >> > > > $1.apply(ManyToMany.scala:54)
>
> >> net.liftweb.mapper.ManyToMany$MappedManyToMany$$anonfun$children
> >> > > > $1.apply(ManyToMany.scala:54)
> >> > > > scala.List.map(List.scala:812)
> >> > > > net.liftweb.mapper.ManyToMany$MappedManyToMany.children
> >> > > > (ManyToMany.scala:54)
> >> > > > net.liftweb.mapper.ManyToMany$MappedManyToMany.elements
> >> > > > (ManyToMany.scala:96)
> >> > > > scala.Seq$class.flatMap(Seq.scala:293)
> >> > > > net.liftweb.mapper.ManyToMany$MappedManyToMany.flatMap
> >> > > > (ManyToMany.scala:44)
>
> >> > > > def edit(ns: NodeSeq): NodeSeq = {
> >> > > > val theUser = view.entity
> >> > > > val addRole = TheBindParam("insert", view.snippet.link("edit",
> >> ()
> >> > > > => theUser.roles += new Role, Text(S?("Add Role"))))
>
> >> > > > bind("user", ns,
> >> > > > "firstname" -> text(theUser.firstName.is,
> >> theUser.firstName
> >> > > > (_), ("size","20")),
> >> > > > "lastname" -> text(theUser.lastName.is
> >> ,theUser.lastName(_),
> >> > > > ("size", "30")),
> >> > > > "roles" -> theUser.roles.flatMap{role =>
> >> > > > bind("role", ns,
> >> > > > "name" -> role.name.toForm,
> >> > > > "remove" -> SHtml.submit(S?("Remove"), ()=>
> >> > > > theUser.roles -= role)
> >> > > > )
> >> > > > },
> >> > > > addRole,
> >> > > > "submit" -> SHtml.submit(S?("Save"), ()=>view.save)
> >> > > > )
> >> > > > }
>
> >> > > > The offending code seems to be the line: "roles" ->
> >> > > > theUser.roles.flatMap{....
> >> > > > in the above bind method when I click on the addRole link.
>
> >> > > > Here's my User class:
>
> >> > > > class User extends MegaProtoUser[User] with ManyToMany[Long,User]{
> >> > > > def getSingleton = User // what's the "meta" server
>
> >> > > > object roles
> >> > > > extends MappedManyToMany(UserRole, UserRole.user, UserRole.role,
> >> > > > Role)
>
> >> > > > }
>
> >> > > > What am I doing wrong? You can see how difficult it is to slog
> >> through
> >> > > > this code, let alone just
> >> > > > trying to explain the problem so I can get help.
>
> >> > > > On Aug 5, 9:57 am, Naftoli Gugenheim <[email protected]> wrote:
>
> >> > > > > I'll try.
> >> > > > > By the way, as per my correction, you can implement list the
> >> regular
> >> > > way without ModelView, and just use ModelSnippet's load function in
> >> your
> >> > > edit link or button, passing it the User instance.
>
> >> > > > > -------------------------------------
>
> >> > > > > glenn<[email protected]> wrote:
>
> >> > > > > Naftoli,
>
> >> > > > > I fixed my code per your comments and now I can edit and remove
> >> users
> >> > > > > from a list, as long as I populate the list with
> >> > > > > ModelView instances, as you said. As for the docs, this step was
> >> not
> >> > > > > clear to me at all. I just assumed that the list was
> >> > > > > just populated with User entities and the view in the ModelSnippet
> >> was
> >> > > > > instantiated with the selected User on each request.
>
> >> > > > > It sounds like your plate is pretty full, so I won't expect much,
> >> but
> >> > > > > sometime soon, could you provide an example, or improved
> >> > > > > docs, for using TableEditor and its related ItemsList trait.
>
> >> > > > > Thanks for all.
>
> >> > > > > Glenn...
>
> >> > > > > On Aug 5, 9:18 am, Naftoli Gugenheim <[email protected]>
> >> wrote:
>
> >> > > > > > Correction: ModelSnippet.load takes the actual Mapper instance,
> >> not
> >> > > the ModelView wrapper.
>
> >> > > > > > -------------------------------------
>
> >> > > > > > Naftoli Gugenheim<[email protected]> wrote:
>
> >> > > > > > To answer your immediate question, the listing should not refer
> >> to
> >> > > the snippet's view but new ModelView instances for each entity. Then
> >> > > editAction is shorthand for the snippet's link method with a callback
> >> to
> >> > > call load on the ModelView. To set the snippet's view's entity, either
> >> call
> >> > > load on the snippet with the other ModelView, or call load on the
> >> other
> >> > > ModelView (or just set its entity directly).
> >> > > > > > As far as documentation, please tell me what scaladocs need what
> >> > > clarification. Thanks.
>
> >> > > > > > -------------------------------------
>
> >> > > > > > glenn<[email protected]> wrote:
>
> >> > > > > > Naftoli,
>
> >> > > > > > Functional programming systems are notoriously difficult to
> >> document.
>
> ...
>
> read more »
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