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Boot.scala in lift..

Answer 1

+5 A:

Looks like you're trying to build a list with cons without having an empty list at the end. Try this instead

val entries = Menu(Loc("Home", List("index"), "Home")) ::
Menu(Loc("StudentLogin", List("studentlogin"), "Student Login"))  ::
Menu(Loc("ProviderLogin", List("providerlogin"), "Provider Login")) :: 
Nil

LiftRules.setSiteMap(SiteMap(entries :_*))

Joe 2009-10-08 15:55:11

Thanks Joe, just figured this out myself. If you have a sec, assuming you get it, could you explain why the Nil is necessary?Thanks.

2009-10-08 16:03:16

The :: operator works on lists. Nil is an empty list

Willem 2009-10-08 16:45:10

But why is the nil required to finish the list?

2009-10-08 17:40:11

It's to do with the way that lists are theoretically represented. In functional languages such as Haskell, LISP and Scala, the List is a recursive data structure. It's formed with recursive applications of `cons` (in Scala it looks like `::`) which combines a single element (on the left hand side) with a list (on the right hand side) to give a list. There must be a list on the right hand side, that's just how `cons` works. `Nil` means 'empty list', and it's always required to terminate your list declaration. This is an important, fundamental aspect of FP and Scala which you should understand!

Joe 2009-10-08 19:12:56

Thanks Joe. That makes a lot of sense.

2009-10-08 20:43:52

in general, any operator that ends with colon (":") in Scala is right associative. So x + y is equivalent to x.+(Y), because "+" is left-associative, but x abc: y is equivalent to y.abc:(x) ....

LES2 2010-01-22 15:58:15

Answer 2

+1 A:

Not using the :: operator might be more readable:

val entries = List(Menu(Loc("Home", 
                        List("index"), "Home")),
                   Menu(Loc("StudentLogin", 
                        List("studentlogin"), "Student Login")),
                   Menu(Loc("ProviderLogin", 
                        List("providerlogin"), "Provider Login")))

Willem 2009-10-08 16:44:04

Makes it less readable, even with the formatting. Had he formatted it better it would read better then yours.

Jim Barrows 2009-12-29 16:17:27

Answer 3

+3 A:

Please take a look at the SiteMap wiki page as well: http://liftweb.assembla.com/wiki/show/liftweb/SiteMap

The new and improved SiteMap syntax is:

def siteMap() = SiteMap(
  Menu(S ? "Home") / "index",
  Menu(S ? "About") / "about" / "index" submenus (
    Menu(S ? "Management") / "about" / "management",
    Menu(S ? "Goals") / "about" / "goals"),
  Menu("directions", S ? "Directions") / "directions" >> Hidden,
  Menu(S ? "Admin") / "admin" / "index" >> If(loggedIn_?, "You must be logged in"))

David Pollak 2010-06-18 05:33:34

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