In the interest of sharing ideas with the larger Lift community, I
found myself creating many different mapper classes to model a
hierarchy of entities best viewed in a tree, such as roles, tags and
navigation links. To reduce code duplication, and to try to better
understand Mapper classes, I went about creating a tree item mapper
trait and its companion meta mapper object.
I defined the item mapper as:
trait MegaTreeItem[T <: MegaTreeItem[T]] extends KeyedMapper[Long, T]
{ .. }
which has a parent (owner) metamapper object of type T, an itemName
MappedString and some useful, though not an exhaustive number of
functions.
and the meta mapper
trait MetaMegaTreeItem[ModelType <: MegaTreeItem[ModelType]] extends
KeyedMetaMapper[Long, ModelType] {..}
which contains menu Locs and template/snippet functions for list and
tree table display.
So, creating a tag mapper is a cinch:
object Tag extends Tag with MetaMegaTreeItem[Tag] {
}
class Tag extends MegaTreeItem[Tag]{
def getSingleton = Tag
def owner = Tag
}
I'm still mystified about the workings of Mappers and MetaMappers and
why creating new mapper traits has to be so wordy (maybe not, if I
understood better), but this does do the job.
You can see the code and all of this actually functioning (Yeah!), by
grabbing it on github, at
http://github.com/glennSilverman/democritus
Disclaimer: I could not get the tree table to work in IE 8. I think
it's a problem with the JQuery javascript. It works
great in Firefox, however.
Glenn
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