Hi,
Small update.
Changing the order of the comparison in my code
i.e. b.author == 1 instead of 1 == b.author
fixed the warning, but I'm still curious as to whether what I'm doing
is a good idea.
Thanks.
Cheers,
Achint
On Mar 6, 2:14 pm, Achint Sandhu <achint.san...@gmail.com> wrote:
> Hi,
>
> I've run into a slight snag with my use of the current approach. I
> suspect what I'm trying to do is silly. The interaction below is from
> the lift console and I don't actually use open_! in my code.
>
> ---
> scala> val b = Book.find(1).open_!
> l: com......Book = com......Book={id=1,author=1}
>
> scala> b.author
> res3: b.author.type = 1
>
> scala> b.author == 1
> res4: Boolean = true
> ---
>
> If for some reason a Book does not have an author (possible in my
> applications case), b.author would return NULL and comparing b.author
> == 1 returns Boolean = false
>
> This approach works in the actual application, but the compiler
> generates the following warning.
>
> ---
> warning: comparing values of types Long and object b.author using `=='
> will always yield false
> ---
>
> In the specific application case I have, I have access to the
> Author.id and want to check if the book is referring to the author
> whose ID I have before I do something. I know that I could look up the
> Author object and do the comparison, but the above seemed to be a
> useful shortcut.
>
> Is there a recommended (succinct) way of accomplishing the above ?
>
> I'd like the thank everyone for the patience and help provided so far.
>
> Cheers,
> Achint
>
> On Mar 2, 3:26 pm, Mads Hartmann Jensen <mads...@gmail.com> 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
>
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