Re: Better way to implement reverse mapping of custom enum ordinals?

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 19 Dec 2009 20:22:45 -0800

Message-ID:

<lEhXm.35994$gd1.3472@newsfe05.iad>

Lew wrote:

Daniel Pitts wrote:

  // Exposing this as a public final field.
  // One of the few times I would actually do that.
  public final int columnValue;

markspace wrote:

This bit here I had to comment on. The whole point of enums is that
you replace int, which is a homogeneous type that appears everywhere
in a program, with a specific class type, which only appears in your
API where it is a valid parameter.

The idea that you then goes back in the other direction and use enums
to store a public integer value... ow! brain hurt bad...

But it's a type-safe int!

Actually, the way I see it is the public integer is an *external* key.
It is not controlled by the program, and therefor must be declared as a
magic number somewhere. The fact that it is being converted to and from
type-safe enums is at least a partial win. The best practices for
this situation would be to maintain the enum value for as much of the
time as possible.

For better control over this "best practice", it might make more sense
to make that a package protected value, and force the data-access code
to do the conversions immediately after read, and prior to write.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>