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 <gl...@exmbly.com> 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 <naftoli...@gmail.com> 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<gl...@exmbly.com> 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 <naftoli...@gmail.com> 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<gl...@exmbly.com> 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 <naftoli...@gmail.com> wrote:
> >
> > > > Correction: ModelSnippet.load takes the actual Mapper instance, not
> the ModelView wrapper.
> >
> > > > -------------------------------------
> >
> > > > Naftoli Gugenheim<naftoli...@gmail.com> 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<gl...@exmbly.com> wrote:
> >
> > > > Naftoli,
> >
> > > > Functional programming systems are notoriously difficult to document.
> > > > The only way to really know what's going on is to meticulously trace
> > > > through the source. But that requires
> > > > time-consuming trial and error coding. So, without clear examples
> > > > demonstrating exactly what you have in mind, I and others in the same
> > > > boat, could spend days and still not
> > > > get it right.
> >
> > > > For example, I tried this:
> >
> > > > var theUser:User = null
> > > > val view = new ModelView(theUser, this)
> >
> > > > def list(ns: NodeSeq): NodeSeq = User.currentUser.map({user =>
> > > > User.findAll.flatMap({u =>
> > > > bind("user", chooseTemplate("user", "entry", ns),
> > > > "firstname" -> Text(u.firstName.is),
> > > > "lastname" -> Text(u.lastName.is),
> > > > "email" -> Text(u.email.is),
> > > > "roles" -> u.roles.map(_.name.toString).mkString(",
> > > > "),
> > > > view.editAction,
> > > > view.removeAction
> > > > )
> > > > })
> > > > }) openOr Text("You're not logged in")
> >
> > > > and, I get a null value exception when I try to remove a user in the
> > > > list. Simply using
> > > > val view = new ModelView(new User, this), doesn't work either,
> > > > although I don't get an
> > > > exception. Now, where should I be calling load in all of this?
> >
> > > > Glenn...
> >
> > > > On Aug 3, 6:22 pm, Naftoli Gugenheim <naftoli...@gmail.com> wrote:
> >
> > > > > Your snippet should extend ModelSnippet (which extends
> StatefulSnippet).
> > > > > Then write:
> > > > > val view = new ModelView(new User, this) {}
> > > > > Calling load on another ModelView that references the snippet will
> load its entity into that view val. It has a number of methods of possible
> interest, like save which checks validity.
> > > > > Also see Util.
> > > > > Are you seeing the scaladocs?
> >
> > > > > -------------------------------------
> >
> > > > > glenn<gl...@exmbly.com> wrote:
> >
> > > > > Just to add to what I just wrote, I don't see how your ModelView
> can
> > > > > be applied to
> > > > > User, which already extends a class, MegaProtoUser. Maybe I'm not
> > > > > comprehending this correctly.
> >
> > > > > Glenn...
> >
> > > > > On Aug 3, 3:48 pm, glenn <gl...@exmbly.com> wrote:
> >
> > > > > > Naftoli,
> >
> > > > > > Liked your OneToMany article, but not sure how the new
> > > > > > ModelView and ModelSnippet code can be applied to ManyToMany.
> > > > > > Can you provide a sample?
> >
> > > > > > Glenn...
> >
> > > > > > On Aug 2, 1:21 pm, Naftoli Gugenheim <naftoli...@gmail.com>
> wrote:
> >
> > > > > > > I put an article on the wiki about OneToMany --
> http://wiki.github.com/dpp/liftweb/how-to-work-with-one-to-many-relat...
> > > > > > > .
> >
> > > > > > > On Sun, Aug 2, 2009 at 11:20 AM, Naftoli Gugenheim <
> naftoli...@gmail.com>wrote:
> >
> > > > > > > > Glad to hear. Also see mapper.view.ItemsList (anyone have a
> better name?),
> > > > > > > > which is used byTableEditor. It's a similar idea without
> relationships.
> > > > > > > > Should MappedOne/ManyToMany be based on ItemsList?
> > > > > > > > Also should I take Mapped out of those names? After all,
> they're not
> > > > > > > > MappedFields and they don't correspond to a table column.
> >
> > > > > > > > -------------------------------------
> > > > > > > > Magnus Alvestad<magnus.alves...@gmail.com> wrote:
> >
> > > > > > > > This work that you've done in Mapper fits in very well with
> something
> > > > > > > > I've been planning to do. In a Java project some time ago we
> > > > > > > > implemented a 'change engine'. We were loading big pension
> agreements,
> > > > > > > > manipulating them in a web interface and finally saving them
> back to
> > > > > > > > the database. While the user was working on the agreement, we
> > > > > > > > generated a list of changes, containing enough information to
> replay
> > > > > > > > or unroll the change. We could use this to implement undo and
> some
> > > > > > > > semi-intelligent merging when two users were trying to commit
> changes
> > > > > > > > to the same agreement. We also let the user review his
> changes before
> > > > > > > > saving, and we indicated changed fields visually. We were
> even
> > > > > > > > thinking of implementing some kind of macro or replay
> functionality,
> > > > > > > > but never got that far.
> >
> > > > > > > > I've been trying to implement something similar as a lift
> component,
> > > > > > > > but with the old relationship handling it wasn't practical.
> With your
> > > > > > > > changes it should be. Thanks!
> >
> > > > > > > > -Magnus
> >
> > > > > > > > On Jul 27, 9:57 pm, Naftoli Gugenheim <naftoli...@gmail.com>
> wrote:
> > > > > > > > > I committed some code last night, which can help building
> mapper-based
> > > > > > > > view snippets, with G-d's help. It includes the following
> classes:
> > > > > > > > > (1-2) net.liftweb.mapper.OneToMany, ManyToMany: Gives a
> more
> > > > > > > > object-oriented approach to managing related entites. You can
> manage the
> > > > > > > > many side of a 1-n and n-n as a mutable collection of
> children, and the
> > > > > > > > parent of a child can be set directly, instead of via its id.
> And the
> > > > > > > > children are not saved to the database when you add them
> until you call save
> > > > > > > > on it or its parent, nor deleted when you remove tem until
> you call
> > > > > > > > delete_!, which is very helpful when you need to keep track
> of adds/removes
> > > > > > > > through multiple requests. For example, if you are displaying
> a list and you
> > > > > > > > can click delete, but it shouldn't be permanently deleted
> until you click
> > > > > > > > save.
> > > > > > > > > There is a new package, ...mapper.view, which contains a
> number of
> > > > > > > > utilities for mapper-based views:
> > > > > > > > > (3-4) ModelView and ModelSnippet provide a number of
> building blocks for
> > > > > > > > views that are too complex to CRUDify. Inherit ModelSnippet
> (which extends
> > > > > > > > StatefulSnippet) and wrap your entities in ModelView (view is
> used in the
> > > > > > > > sense of a wrapper).
> > > > > > > > > (5) Util provides some more building blocks that just be
> imported,
> > > > > > > > without needing a ModelSnippet context.
> > > > > > > > > (6-7) Paginator makes it easy to create paginated, user
> sortable
> > > > > > > > listings. You can use PaginatedSnippet instead of
> ModelSnippet to help.
> > > > > > > > > (8-10) ItemsList lets you manage a list of entities with
> pending
> > > > > > > > additions and deletions. It's used byTableEditor, which is a
> very easy to
> > > > > > > > use and customizable snippet to edit tables directly. It's
> useful for
> > > > > > > > editing short lists, e.g., a lookup table like cities. Don't
> forget to
> > > > > > > > register the table in Boot.
> > > > > > > > > (11) Then there's the experimental FormProcessor, if you
> need your form
> > > > > > > > to be processed in one block instead of separate closures,
> e.g., to surround
> > > > > > > > with try.
> > > > > > > > > (12) Also experimental is sitemap.XmlMenu which lets you
> write menus in
> > > > > > > > xml.
> > > > > > > > > (13) I may add CaseEnum, which lets you write case classes
> that
> > > > > > > > automatically double as an Enumeration.
> > > > > > > > > Questions, comments, suggestions, and constructive
> criticism are more
> > > > > > > > than welcome!
> > > > > > > > > Thanks.
> >
>
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