Re: bindings tutorial doesn't work
Re: bindings tutorial doesn't work
- Subject: Re: bindings tutorial doesn't work
- From: Daniel Child <email@hidden>
- Date: Tue, 20 May 2008 11:27:03 -0400
THANK YOU!
On May 20, 2008, at 9:33 AM, Michael Babin wrote:
On May 19, 2008, at 11:41 PM, Daniel Child wrote:
After reading a host of theoretical explanations on bindings, I
tried the bindings-based currency converter tutorial to try to get
some basic feel for bindings in practice. The example is written
for an earlier version of OSX, but I think I reproduced it
correctly for XCode 3. However, I get the following runtime error.
Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: 'Cannot create number
from object <_NSControllerObjectProxy: 0x148070> of class
_NSControllerObjectProxy'
I am surprised by the error because bindings is supposed to be
"smart enough" to convert the numbers in text fields (strings) to
numbers when necessary. For those who haven't seen the tutorial,
the interface is:
@interface Converter : NSObject
{
double dollarsToConvert;
double exchangeRate;
}
-(double) amountInOtherCurrency;
// implemented as return (double) (dollarsToConvert * exchangeRate)
@end
I have no idea what this error means and found no helpful
references on the web. If someone could shed some light on this
issue I'd really appreciate it. Thanks.
You probably don't have the Model Key Path of the Value binding for
one of your text fields set correctly. Without it, you're binding
the text field's value to the object controller's selection (your
Converter object), instead of one of Converter's keys (exchangeRate,
dollarsToConvert, amountInOtherCurrency). The error is complaining
that it doesn't know how to create a number from your Converter
object. The NSControllerObjectProxy is a proxy object (see NSProxy)
returned by the object controller to represent the actual object
(Converter) which you set as the object controller's content.
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