Tuesday, December 28, 2010

Easier object inspection in the Scala REPL

If you're like me, you spend a fair amount of time poking at objects of poorly documented classes in a REPL (Scala or otherwise...). This is great compared to writing whole test programs solely for the purpose of seeing what something does or what data it really contains, but it can be quite time consuming. So I've written a utility for use on the Scala REPL that will print out all of the "attributes" of an object. Here's some sample usage:

scala> import replutils._
import replutils._

scala> case class Test(a: CharSequence, b: Int)
defined class Test

scala> val t = Test("hello", 1)
t: Test = Test(hello,1)

scala> printAttrValues(t)
hashCode: int = -229308731
b: int = 1
a: CharSequence (String) = hello
productArity: int = 2
getClass: Class = class line0$object$$iw$$iw$Test

That looks fairly anti-climatic, but after spending hours typing objName. to see what's there, and poking at methods, it seems like a miracle. Also, one neat feature of it is that if the class of the object returned is different from the class declared on the method, it prints both the declared class and the actual returned class.

Code and further usage instructions is available on BitBucket here.

So what exactly is an attribute?

I haven't quite figured that out yet. Right now it is any method that meets the following criteria:

  1. the method has zero arguments
  2. the method is public
  3. the method is not static
  4. the method's name is not on the exclude list (e.g. wait)
  5. the method's return type is not on the exclude list (e.g. Unit/void)
  6. the method is not a "default argument" method
Please post any feedback in the comments here, or better yet in the issue tracker on Bitbucket.

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1 comment:

olsonsfoodemporium said...

It won't really have success, I consider so.