As others may have said, the difference between a Box and a value that may be
null is that both may or may not contain what you want it to have; but in one
case the compiler lets you assume that it does--that it's not null--which is a
source of many bugs.
Programming presents a tension between type safety and conciseness, and Scala
does an amazing job of being extremely type safe and extremely concise. But
type safety comes first.
-------------------------------------
DMB<combust...@gmail.com> wrote:
I guess that could work, but why go to such lengths where there are
much more straightforward solutions available? What do for
comprehensions buy you in this case? I mean, 99% of the time, when I
want to check for a cookie, I don't need the cookie itself or any of
its properties. I need its value, or null if there's no cookie. Why
not do something a-la RoR:
S.cookieValue("cookieName")
or a-la ASP.NET:
val c = S.cookie("cookieName")
if(c != null) {
val v = c.value
}
Or, indeed, both?
On Nov 16, 1:22 am, Sergey Andreev <andser...@gmail.com> wrote:
> Hi,
>
> For-comprehensions could help you out:
>
> for{
> cookie <- S.findCookie(cookieName)
> value <- cookie} doSomethingWithValue
>
> Regards
>
> On Mon, Nov 16, 2009 at 12:07 PM, DMB <combust...@gmail.com> wrote:
>
> > When I call findCookie it returns a Box. Then, the value on the cookie
> > itself is also a box. Hence a ruby one-liner turns into something
> > like:
>
> > val cookie = S.findCookie(cookieName)
> > if(cookie.isDefined) {
> > val cookieVal = cookie.open_!.value.openOr(null)
> > // Do something with the cookie value
> > }
>
> > This is very ugly, so I'm guessing I'm doing something wrong, but try
> > as I might, I could not find any examples that would look even vaguely
> > "right" to me.
>
> > Why can't findCookie return a simple, unboxed HTTPCookie object or
> > null if cookie is not found?
> > Why does the value inside a cookie need to also be Box'ed?
>
> > For the sake of comparison, here's how you do the same thing in RoR:
> > v = cookies["cookieName"]
> > // Do something with the cookie
>
> > or ASP.NET:
> > var c = Request.Cookies["CookieName"]
> > if(c != null) {
> > var v = c.Value
> > // Do something with the cookie
> > }
>
> > I fail to see why Lift should be more complicated.
>
> > This is with Lift 1.1 M7
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