On 03/14/2011 03:46 PM, Alexey Zinger wrote:
I see a small problem with the Scala stuff. Specifically:
FileRef
- DirectoryFileRef
- StreamableFileRef
- AppendableFileRef
- RandomAccessFileRef
- NonExistantFileRef
How does this address the scenario of a non-existent file reference
"becoming" existent by a side-effect of code elsewhere (maybe outside
current execution thread, or the JVM as a whole)?
In fact, this should be handled with composition rather than
inheritance, and dynamic composition (I mean, in my example I have a
FileModel which is pretty "static" and only exposes getPath(), and then
you can search in it roles such as Removable, Readable, Writable, etc...
Roles might be present or not in function of the current state of the
object. It's another interesting discussion, in my perspective is how to
implement DCI. While Java is easily (and rightfully) blamed for the lack
of mixins, that seem to help, indeed mixins only allow to work
statically. In the end, a dynamic solution doesn't require any specific
language support, with the exception of some sugar. But this is a
digression from the original topic.
But in general, this just feels like a losing battle to me -- trying
to apply immutability principles to I/O. Why?
Because since it's a known immutability problem, it's a good testcase to
discuss how immutability faces with the real world. The idea is not to
find a "solution", which probably doesnt' exist, but the best trade off.
--
Fabrizio Giudici - Java Architect, Project Manager
Tidalwave s.a.s. - "We make Java work. Everywhere."
java.net/blog/fabriziogiudici - www.tidalwave.it/people
[email protected]
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