On Sat, Oct 3, 2009 at 11:33 AM, Peter Robinett <pe...@bubblefoundry.com> wrote:
>
>
> On Oct 3, 12:04 pm, Kevin Wright <kev.lee.wri...@googlemail.com>
> wrote:
>> On Sat, Oct 3, 2009 at 10:43 AM, Peter Robinett <pe...@bubblefoundry.com>
>> wrote:
>>
>> > Thanks, Kevin. I'm going to poke around with lift-json a bit more but
>> > a case class may be the way to go.
>>
>> case classes definitely get you some juicy extras, it becomes a lot
>> easier to filter or map a list of readings when compared to the raw
>> json.
>
> Great.
>> You might also want to look at record/mapper if database persistence
>> is your thing...
>
> Hence the original question, whether I could use extract to get
> instances of my Mapper model. ;-) Case classes would just add another
> step in the translation, but it looks like it's both necessary and
> easy.
Ahh, I misinterpreted Mapper as Map - a very different beast :)
You could always use the JsonTempReading extractor from above to
directly build a Mapper class instead of a case class.
Having said that... going via a case class here would allow some
benefits, such as performing json decoding and mapper validation as
independent operations. The first pass would use the extractor to
return an Option[TempReading], the second pass would then map this to
a Box - with the error condition being used if there's a validation
failure. This arrangement should also be easier to test and debug, I
think that separating multiple steps like this is generally a Good
Thing, especially in the realms of functional programming.
>> I'm with DavidP on this one, get as much rich type info into the
>> system at the earliest opportunity. A timestamp definitely carries
>> more semantic meaning than a number. Imagine trying to filter the 30
>> days worth of readings that were taken between 9am and 5pm GMT (when
>> your server is running on EST)
>
> Good point. Do you know of any sample Mapper code that uses scala-
> time? I'm still not very strong with making my own mapped types.
I've not yet used both libraries at the same time, though I do
remember some discussion a while back about doing exactly this.
Probably worth a search back through the group messages, but I'm
pretty sure it's not difficult to do.
> Peter
>
>> > Peter
>>
>> > On Oct 3, 11:13 am, Kevin Wright <kev.lee.wri...@googlemail.com>
>> > wrote:
>> >> Sounds to me like you want to create yourself a small helper function
>> >> that can map that structure into your own case class, something like:
>>
>> >> case class TempReading(node:String, dt:Int, temp:Double)
>>
>> >> It should be possible to do this as a layer on top of the json parser.
>> >> So you can go from:
>>
>> >> Object(
>> >> List(
>> >> JField(node,JString(00:1D:C9:00:04:9F)),
>> >> JField(dt,JInt(1254553581405)),
>> >> JField(temp,JDouble(27.5))
>> >> )
>> >> )
>>
>> >> to:
>>
>> >> TempReading("00:1D:C9:00:04:9F", 1254553581405, 27.5)
>>
>> >> A Map would be an improvement over the raw json, but still is nowhere
>> >> near as concise or type-safe as the dedicated structure.
>>
>> >> You probably also want to rethink using ints for datetime (I guess
>> >> this is what dt represents). Take a look at the scala-time library,
>> >> which is a nice wrapper over Java's joda-time.
>>
>> >> On Sat, Oct 3, 2009 at 9:46 AM, Peter Robinett <pe...@bubblefoundry.com>
>> >> wrote:
>>
>> >> > I guess this is basically a question for Joni, but I figure I'll throw
>> >> > it out here for everyone to see.
>>
>> >> > Would it be possible to have extract() support Mapper instances in
>> >> > additional to standard case classes?
>>
>> >> > After parsing some JSON I get the following JValue: JObject(List(JField
>> >> > (node,JString(00:1D:C9:00:04:9F)), JField(dt,JInt(1254553581405)),
>> >> > JField(temp,JDouble(27.5)))). I'd like to turn this into a new
>> >> > instance of my Packet model and it'd be awesome if extract could do
>> >> > that.
>>
>> >> > I don't know how hard would it be to add this feature, so I don't know
>> >> > if this is a reasonable request. This would make making JSON API
>> >> > endpoints really easy for me and I hope for other people too.
>>
>> >> > Peter Robinett
> >
>
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Lift" group.
To post to this group, send email to liftweb@googlegroups.com
To unsubscribe from this group, send email to
liftweb+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/liftweb?hl=en
-~----------~----~----~----~------~----~------~--~---
