Re: Bindings only working in one direction

[Andy Balholm]

In Cocoa, the action seems to be sent when the control loses focus or  
Enter is pressed, regardless of whether the value has actually changed.

In Interface Builder, I made a window with two text fields and a  
slider. Each text field's action is set to takeIntegerValueFrom: and  
its target is the slider. If I put 0 in one field and 100 in the  
other, the slider moves back and forth as I click on the two fields.

Updating the value for a binding, on the other hand, is called from - 
[NSTextField textShouldEndEditing:]. The value is updated only if the  
contents of the field have actually changed. I got the following stack  
trace by binding to a custom class whose setter always crashes:

#0      0x90e7abfa in _objc_error
#1      0x90e7ac30 in __objc_error
#2      0x90e79637 in _freedHandler
#3      0x00001f7f in -[BadSetter setValue:] at BadSetter.m:24
#4      0x909565f4 in _NSSetIntValueAndNotify
#5      0x9089f257 in _NSSetUsingKeyValueSetter
#6      0x9089ecee in -[NSObject(NSKeyValueCoding) setValue:forKey:]
#7      0x909237c1 in -[NSObject(NSKeyValueCoding) setValue:forKeyPath:]
#8	0x94828441 in -[NSBinder  
_setValue:forKeyPath:ofObject:mode:validateImmediately:raisesForNotApplicableKeys:error 
:]
#9      0x948281f2 in -[NSBinder setValue:forBinding:error:]
#10	0x94827e8b in -[NSValueBinder  
_applyObjectValue:forBinding:canRecoverFromErrors:handleErrors:typeOfAlert:discardEditingCallback:otherCallback:callbackContextInfo:didRunAlert 
:]
#11	0x94827b19 in -[NSValueBinder  
applyDisplayedValueHandleErrors:typeOfAlert:canRecoverFromErrors:discardEditingCallback:otherCallback:callbackContextInfo:didRunAlert 
:]
#12	0x9482a86e in -[NSValueBinder  
_applyDisplayedValueIfHasUncommittedChangesWithHandleErrors:typeOfAlert:discardEditingCallback:otherCallback:callbackContextInfo:didRunAlert 
:]
#13	0x948273fa in -[NSValueBinder  
validateAndCommitValueInEditor:editingIsEnding:errorUserInterfaceHandled 
:]
#14	0x948271b7 in -[_NSBindingAdaptor  
_validateAndCommitValueInEditor:editingIsEnding:errorUserInterfaceHandled:bindingAdaptor 
:]
#15	0x948270ef in -[_NSBindingAdaptor  
validateAndCommitValueInEditor:editingIsEnding:errorUserInterfaceHandled 
:]
#16     0x946f9eb1 in -[NSTextField textShouldEndEditing:]
#17     0x946f99ee in -[NSTextView(NSSharing) resignFirstResponder]


Andy Balholm
(509) 276-9718
andy@balholm.com



On Jun 23, 2009, at 1:06 AM, Fred Kiefer wrote:

> Andy Balholm wrote:
> > The bindings in my Company Info window are supposed to be read-write,
> > but they can only read the data from the model. Changes to the text  
> > in
> > the fields do not change the model. I tried taking the bindings out  
> > of
> > the NIB and binding the fields programmatically instead, and it  
> > didn't
> > make any difference. Once again, it works fine under Cocoa, but not
> > under GNUstep.
>
> Support for key value binding is still very limited in GNUstep. Most
> likely we are just missing a call to our internal method
> reverseSetValueFor: here. We are calling this method from [NSControl
> sendAction:to:] and this only gets called when you leave the text  
> fields
> with the return key. In that case the values seem to get properly
> stored. What seems to be missing is a similar call when the field is
> changed by any other way.
> Does anybody know, when we should send the action for a text field?
> Perhaps we have to send that regardless of the way the field gets  
> changed?
>
> Fred