MappedString holding null

[Naftoli Gugenheim]

1. Why does MappedString have members such as nonNull(in: String)
which don't depend on the MappedString's state? Shouldn't they be in a
singleton somewhere?
2. It would be nice if there was a method like 'is' that would return
null as "". Actually for my particular use case where I'm testing
field.is.isEmpty it would be nice if it would have a method like
isEmpty that would return true if value==null || value.isEmpty.

[David Pollak]

On Wed, Oct 14, 2009 at 7:45 PM, Naftoli Gugenheim <nafto...@gmail.com> wrote:

1. Why does MappedString have members such as nonNull(in: String)
which don't depend on the MappedString's state? Shouldn't they be in a
singleton somewhere?

Maybe they should be, but are they hurting anything where they are?
 

2. It would be nice if there was a method like 'is' that would return
null as "". Actually for my particular use case where I'm testing
field.is.isEmpty it would be nice if it would have a method like
isEmpty that would return true if value==null || value.isEmpty.

You can (1) write a trait and mix it in or (2) write a subclass of MappedString and use that.
 

--
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

[Ross Mellgren]

I've been using implicit extensions for this kind of thing, most recently expanded error handling via Box. Like this:

implicit def mappedStringToMappedStringExtension(ms: MappedString): MappedStringExtension = MappedStringExtension(ms)

case class MappedStringExtension(mappedString: MappedString) {

    def orBlank: String = mappedString.is match {

        case null => ""

        case s => s

    }

    def isEmpty: Boolean = mappedString.is match {

        case null => true

        case s if s.length == 0 => true

        case _ => false

    }

}

-Ross

[Naftoli Gugenheim]

Good point, thanks.

[Naftoli Gugenheim]

On Wed, Oct 14, 2009 at 11:08 PM, David Pollak <feeder.of...@gmail.com> wrote:

On Wed, Oct 14, 2009 at 7:45 PM, Naftoli Gugenheim <nafto...@gmail.com> wrote:

1. Why does MappedString have members such as nonNull(in: String)
which don't depend on the MappedString's state? Shouldn't they be in a
singleton somewhere?

Maybe they should be, but are they hurting anything where they are?

Nope! Not complaining, just mentioning it. Are they meant to be public? Are they used with any value for 'in' other than the field's own value? In other words, would it make sense to take off the 'in' parameter, satisfying #1 and #2.

[David Pollak]

On Wed, Oct 14, 2009 at 8:40 PM, Naftoli Gugenheim <nafto...@gmail.com> wrote:

On Wed, Oct 14, 2009 at 11:08 PM, David Pollak <feeder.of...@gmail.com> wrote:

On Wed, Oct 14, 2009 at 7:45 PM, Naftoli Gugenheim <nafto...@gmail.com> wrote:

1. Why does MappedString have members such as nonNull(in: String)
which don't depend on the MappedString's state? Shouldn't they be in a
singleton somewhere?

Maybe they should be, but are they hurting anything where they are?

Nope! Not complaining, just mentioning it. Are they meant to be public? Are they used with any value for 'in' other than the field's own value? In other words, would it make sense to take off the 'in' parameter, satisfying #1 and #2.

If you change their signatures, it will break existing code.  I probably added them when I needed some helper methods.

You're welcome to add companions that read the current "is" value of the MappedString

 

 

2. It would be nice if there was a method like 'is' that would return
null as "". Actually for my particular use case where I'm testing
field.is.isEmpty it would be nice if it would have a method like
isEmpty that would return true if value==null || value.isEmpty.

You can (1) write a trait and mix it in or (2) write a subclass of MappedString and use that.
 

--

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