Hi Jukka,
Good point about nullable Boolean.
I'd like to keep the checkbox, rather than a 3 items combobox,
but I think it will be difficult to add the capability to "nullify" it.
Notice that boolean type is not the only one concerned.
Once you have set a value for a String attribute type, you cannot
nullify it back.
Having null and empty values in a string attribute (or null and false)
is always
very confusing (either in OJ or in a database). A few years ago, I added
the isNull
function in the Simple Query Tool to make some queries just possible.
Michaël
Le 19/03/2015 11:00, Rahkonen Jukka (MML) a écrit :
Hi Michael,
Have you been thinking if OpenJUMP should support NULL as a third
option in Boolean attributes? Right now it seems to partly support
NULLs, partly not.
-Create a new feature, do not edit attributes, save -> Boolean
attributes are saved as NULLs but user probably believes that they are
False because attribute table shows the box unchecked.
-Edit Boolean attribute by checking/unchecking the tick box -> Value
is True or False but it can’t be changed back to NULL
Current behavior does not feel correct. I can imagine two alternatives:
-Deny NULL and initialize all Boolean attributes to False.
-Make some clever change to user interface that makes difference
between the three Boolean values: NULL, TRUE, FALSE. Empty check box
with colored borders for null? Or three-item drop-down menu?
Considerations about what it means on the Java side
http://stackoverflow.com/questions/11185321/when-should-null-values-of-boolean-be-used
dBase format and shapefiles do support NULL
http://www.clicketyclick.dk/databases/xbase/format/data_types.html
-Jukka Rahkonen-
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