Re: Bindings, NSNumber equal to NIL and performing mathematical operations issue
Re: Bindings, NSNumber equal to NIL and performing mathematical operations issue
- Subject: Re: Bindings, NSNumber equal to NIL and performing mathematical operations issue
- From: Ricky Sharp <email@hidden>
- Date: Thu, 5 May 2005 17:19:35 -0500
On May 5, 2005, at 4:52 PM, Eric Hochmeister wrote:
I'm using bindings and I'm having an issue with binding a NSNumber up
to an NSTextField and using this NSNumber to perform mathematical
operations.
ie. I have a simple example, two textfields which are bound to two
NSNumber attributes and another textfield which displays the result of
these two NSNumbers multiplied together.
My issue arises, when I enter valid inputs into both textfields, ie.
10 and 10.. the result is 100... but if I delete 10 from one of the
textfields, the result still stays 100. But if I change the textfield
back to another number it is updated correctly. The issue I'm seeing
is that when my NSNumber is set to nil, and I ask [NSNumber
doubleValue] it's giving me not 0... causing my calculation to be
wrong.
I've pasted my result method below. num1 and num2 are both bound to
the textfield, and result is setup to be updated when num1 or num2
change...
ie. [self setKeys:[NSArray arrayWithObjects:@"num1",@"num2",nil]
triggerChangeNotificationsForDependentKey:@"result"];
Any ideas? What I want is that if nothing is entered in the textfield
instead of saving nil, 0 is saved and the textfield is updated to
display 0 as well.
- (NSNumber*)result;
{
double n1 = [[self num1] doubleValue];
double n2 = [[self num2] doubleValue];
double aTotal = n1 * n2;
return [NSNumber numberWithDouble:aTotal];
}
Note that you should be careful when sending messages to null such
that the return type isn't an object, but some primitive type.
Thus, you should rewrite result to do the guard against num1 and/or
num2 being nil.
Additionally, you should set up the appropriate placeholder values in
your nib file for the two operand text fields.
--
Rick Sharp
Instant Interactive(tm)
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden