Hello, before I get to the question this is my setup:
1) NSTextField ("field")
2) bound to an NSNumber property ("number") of an object.
3) "field" has an NSNumberFormatter attached with all default
values (as set up by IB), except maximum fraction digits is set to
1.
4) "number" can be nil - in fact it is when we start our app.Starting this little app, one can tab into and out-of an the empty field, nothing happens. This as expected and what I want.
When you enter a value and tab out, "number" gets set to the new value. If you now attempt to remove the value by emptying the field you will get formatting error message. This is kind of unexpected as the empty field was fine with the formatter moments ago.
In other words, once the value is set to something non-nil it never can get nil again. I would like to be able to nil out a number by clear a field.
My solution for this is a sub-class of NSNumberFormatter which implements -getObjectValue:forString:range:error: as follows:
- (BOOL)getObjectValue:(out id *)anObject
forString:(NSString *)aString
range:(inout NSRange *)rangep
error:(out NSError **)error
{
BOOL result = [super getObjectValue:anObject forString:aString
range:rangep error:error];
if (!result && ((aString == nil) || ([aString isEqualToString:@""]))) {
*anObject = nil;
result = YES;
}
return result;
}
The docs tell me that I have to feed a valid NSNumber into anObject
when returning YES - nil is valid therefore this should be OK.
The question is: Is this safe? Do I overlook an aspect that I'd better not? Or even better, is there a simpler solution?
Regards Markus -- __________________________________________ Markus Spoettl
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