On Tue, Mar 2, 2010 at 5:09 PM, Achint Sandhu <[email protected]>wrote:
> Hi, > > Is there any reason why aBook.author would not simply return a Box > instead of requiring aBook.author.obj to get the Box ? > > For some background, see http://blog.lostlake.org/index.php?/archives/19-Keeping-the-meaning-with-the-bytes.html In Lift's Mapper fields are not flat collections of bytes like in ActiveRecord, but entities that can control access, format, etc. their values. aBook.author is the field. The field is a MappedLongForeignKey. It has lots and lots of methods on it to get, set, validate, generate forms, etc. To make things a little more convenient, the fields know how to convert themselves to their "raw byte" values. So a MappedLongForeignKey is a MappedField[Long] and knows how to convert itself into a Long. For example: val x: Long = aBook.author // legal But MappedLongForeignKey fields need to be explicitly converted into the object that they are keys to via the .obj method: val author: Box[Author] = aBook.author.obj I guess it would be nice to write a convenience conversion to make: val author: Box[Author] = aBook.author legal. Feel free to open a ticket on this. > I'm sure there is a really good reason for this and I'm just trying to > get an understanding of the underlying reasoning. > > Thanks. > > Cheers, > Achint > > On Mar 2, 3:26 pm, Mads Hartmann Jensen <[email protected]> wrote: > > On 02/03/2010, at 20.56, Achint Sandhu wrote: > > > > > > > > > > > > > Hi, > > > > > I'm new to scala (2.7.7) and lift (2.0-M2) and as a learning > exercise > > > have taken on the translation of an existing rails project into a lift > > > application. > > > > > There are two things I have run into that I'm hoping the more > > > experienced members of the list can give me a hand with: > > > > > 1) Is there a trait in lift that creates and manages an equivalent of > > > the createdAt and updatedAt fields that rails provides? I'm thinking > > > something along the lines of IdPK, but have been unable to find > > > anything. > > > > > 2) I've been following the wiki article on setting up One-to-Many > > > relationships ( > http://wiki.github.com/dpp/liftweb/how-to-work-with-one- > > > to-many-relationships) and am running into a difference in behaviour. > > > Following the example, if I look at anAuthor.books, I get back a List > > > of Book objects, however when I look at aBook.author, I get back a > > > Long with the ID of the Author. I would expect aBook.author to return > > > an Author object. I've copied and pasted the example in the wiki, to > > > make sure that it wasn't my implementation. > > > > You should be able to get the object by calling aBook.author.obj - this > should return a Box[Author] so you could get it like this > > > > aBook.author.obj match { > > case Full(a) => a // do something with the autor > > case Empty => // if the box is empty, handle it somehow > > case _ => // should cover everyhting else, Failure etc > > > > } > > > > Hope it helps > > > > > > > > > Other than that, so far, it's gone extremely well and I was able to > > > get something up and running very quickly which really is a testament > > > to the design of the framework. > > > > > Thanks. > > > > > Cheers, > > > Achint > > > > > -- > > > 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]<liftweb%[email protected]> > . > > > For more options, visit this group athttp:// > 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]<liftweb%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/liftweb?hl=en. > > -- Lift, the simply functional web framework http://liftweb.net Beginning Scala http://www.apress.com/book/view/1430219890 Follow me: http://twitter.com/dpp Surf the harmonics -- 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.
