val l = List(1,2,3)
l.map(x => x * 2) == List(2,4,6)
So map take as its argument a function that transforms every member of the list.
flatmap is similar but instead of the new List *consisting of* the transformed
elements, it consists of the *concatenation* of the results of the function
(which must be concatenatable). So
l.flatmap(x => List(x, x * 2)) == List(1,2) ++ List(2,4) ++ List(3,6) ==
List(1,2,2,4,3,6)
Since bind returns a NodeSeq, if you would return the result of bind from a
function you pass to *map* you would have a List of NodeSeq. Flatmap means
you'll get the NodeSeq for each List element concatenated into one long NodeSeq.
So your code needs to continue
...flatmap { curExpense =>
bind("prefix", expenseTemplate, ...)
}
-------------------------------------
pabraham<[email protected]> wrote:
Hi Adam,
Thanks for your advice. Unfortunately if I paste your code, I get
"error: not found: value expensesformonth".
I need to convert my "m" value to an instance of Month where the ID of
this instance is "m", but I can't work out how.
I then tried this:
def allexpenses(expenseTemplate: NodeSeq): NodeSeq = Expense.findAll(By
(Expense.month,m.toLong)).flatmap
but the findAll() gives a List[] not a flatmap, and my Scala isn't
good enough to convert from one to the other!
Regards,
Paul.
On 18 Jan, 08:32, Adam Warski <[email protected]> wrote:
> Hello,
>
>
>
> > I have HTML to print out expenses for a given month (i.e. URL = .../
> > month/12):
>
> > <lift:MonthPage.summary>
> > ...
> > <thismonth:expenseitem>
> > <tr>
> > <td><month:item /></td>
> > <td align="right"><month:amount /></td>
> > </tr>
> > </thismonth:expenseitem>
> > ...
> > </lift:MonthPage.summary>
>
> > The area I'm having problems with is the code to drive the above
> > HTML. I need something like:
>
> > class MonthPage {
> > def summary( xhtml : NodeSeq ) : NodeSeq = S.param("month") match {
> > case Full(m) => {
> > val allexpenses : NodeSeq = expensesformonth.flatmap({ month =>
> > bind("month", chooseTemplate("thismonth", "expenseitem",
> > xhtml),
> > "name" -> Text( month.item ),
> > "amount" -> Text( month.amount )
> > )
> > })
> > bind("thismonth", xhtml, "expenseitem" -> allexpenses)
> > }
> > case _ => {
> > Text( "Not a valid month." )
> > }
> > }
> > }
>
> I think you're almost there.
> Try making the "allexpenses" val a function (def) NodeSeq => NodeSeq. The
> function takes the "template" of the month and returns it with bound values.
> So something like:
>
> class MonthPage {
> def summary( xhtml : NodeSeq ) : NodeSeq = S.param("month") match {
> case Full(m) => {
> def allexpenses(expenseTemplate: NodeSeq): NodeSeq =
> expensesformonth.flatmap({ month =>
> bind("month", expenseTemplate,
> "name" -> Text( month.item ),
> "amount" -> Text( month.amount )
> )
> })
> bind("thismonth", xhtml, "expenseitem" -> allexpenses _)
> }
> case _ => {
> Text( "Not a valid month." )
> }
> }
>
> }
>
> No need to lookup the right template then using chooseTemplate, as the method
> receives the appropriate xhtml.
>
> --
> Adam
--
You received this message because you are subscribed to the Google Groups
"Lift" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/liftweb?hl=en.
--
You received this message because you are subscribed to the Google Groups
"Lift" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/liftweb?hl=en.
