Re: Subclass final class (Boolean) ?
Re: Subclass final class (Boolean) ?
- Subject: Re: Subclass final class (Boolean) ?
- From: Ken Anderson <email@hidden>
- Date: Mon, 28 Aug 2006 07:23:44 -0400
You're absolutely right Kieran - it's my concern too, and I plan on
doing a lot of testing to see what occurs before actually using it :)
Ken
On Aug 27, 2006, at 10:59 PM, Kieran Kelleher wrote:
Correct me if I am wrong, but I have a hunch that one caveat of
using this strategy instead of the custom attribute with factory
and conversion methods is that EOQualifiers (for example in a Fetch
Specification) on this attribute may not "just work" .... it might
be worth verifying before you become too dependent on this strategy
only to find later you might not be able write effective
EOQualifiers on this attribute. With the "true/false" custom
attribute as described in Chuck's book, you can use Boolean.TRUE in
a qualifier on the attribute and it does "just work" .... keeping
in mind that the same Boolean EOQualifier works in an in-memory
array of EO's and a database fetch where EOF auto-generates the SQL
WHERE x='true' or x='false' on the CHAR(5) field.
Regards, Kieran
On Aug 27, 2006, at 1:32 PM, Ken Anderson wrote:
In case anyone else is interested, here's my current solution. I
modified the EOGenerator template for attributes like this:
<$foreach Attribute classAttributes.@sortedNameArray do$>
<$if Attribute.prototypeName eq 'boolean'$>
public Boolean <$Attribute.name$>() {
Integer storedValue = (Integer) storedValueForKey("<
$Attribute.name$>");
if (storedValue.intValue() > 0)
return new Boolean(true);
else
return new Boolean(false);
}
public void set<$Attribute.name.initialCapitalString$>(Boolean
aVal) {
if (aVal.booleanValue())
takeStoredValueForKey(new Integer(1), "<$Attribute.name$>");
else
takeStoredValueForKey(new Integer(0), "<$Attribute.name$>");
}
<$else$>
public <$Attribute.javaValueClassName$> <$Attribute.name$>() {
return (<$Attribute.javaValueClassName$>)storedValueForKey
("<$Attribute.name$>");
}
public void set<$Attribute.name.initialCapitalString$>(<
$Attribute.javaValueClassName$> aValue) {
takeStoredValueForKey(aValue, "<$Attribute.name$>");
}<$endif$>
This change assumes that you have a prototype called boolean, but
besides that, it's pretty generic and has worked well so far :)
Ken
On Aug 27, 2006, at 11:47 AM, Ken Anderson wrote:
Hey Steve...
I think you miss my intention. I don't want to have tons of
subclasses, I simply want to have a boolean in the database that
returns a boolean object in EOGenerator without writing code for
all of them. I'd really rather not hold my nose :)
I always liked Chuck's solution of creating a custom type in
EOModeler that could go to/from booleans using a varchar(5) field
in the database, but just can't get around the amount of space
it's taking up. This endeavor was to try and get the no-code
solution without storing 5 characters in the database.
If you're not familiar, the solution in Practical WebObjects is
to create a custom internal data type with a class of
java.lang.Boolean, a factory method of valueOf, and a conversion
method of toString(). This gets you booleans the way you want
them in java from your DB, no code.
Ken
On Aug 27, 2006, at 11:40 AM, Steve Quirk wrote:
On Sun, 27 Aug 2006, Ken Anderson wrote:
OK, I'm a little annoyed here because I find the whole concept
of 'final' to be ridiculous.
I would like to subclass Boolean so that I can initialize it
(class method) with a short string (valueOf:"t" instead of
valueOf:"f") and also to return "t" and "f" for toString (or
some other method like toShortString()).
Unfortunately, java.lang.Boolean is marked as final. Is there
any way to get around that?
To give a little background, I would like to have a custom
WebObjects type where I can declare the factory method to
create the instance, and the method to call to get back the
string instance. I want to make it a single character so that
I can use a string field with length=1 instead of length=5
(saving a lot of space).
Oh, and yet another reason I want categories from Objective-C
in Java...
Thanks,
Ken
Hi Ken,
For a more complex class with several values, it might make
sense (a single letter indicating eye color, for instance). But
DBs have lots of examples with a two-value true/false column -
all in the same schema.
What do you do for the other tables in your DB that use 1 and 0
(Number) or 'Y'/'N' (char(1)) or 'A'/'D' (char(1) -
"Alive"/"Dead") to represent true and false? A dozen subclasses
of Boolean in the same app? Your coworkers and those who follow
you to maintain your app will be grabbing the pitchforks and
lighting the torches to come & hunt you.
Just give in and do what everyone else does. In your entity
class, hold your nose and code something like:
private static final Character TRUE = new Character('t');
private static final Character FALSE = new Character('f');
boolean rancid; // column RANCID char(1), 't' = TRUE
public void setRancid(boolean aBool) {
value = aBool;
}
public void setRancid(Character aChar) {
setRancid(TRUE.equals(aChar));
}
public Character getRancid() {
return (rancid) ? TRUE : FALSE;
}
public boolean isRancid() {
return rancid;
}
...
TRUE/FALSE is just too easy to code around. Keeping the simple
things final might not be a bad idea.
- sq
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