>From: [EMAIL PROTECTED]>To: [email protected]>Subject: Validating a
>non-optional transient Core Data property - it can be erased?!>Date: Wed, 12
>Nov 2008 22:31:02 +0100>
>In my Core Data database I have a property called 'target' (double), which is
>transient and required (i.e. 'non-optional' in the model). It is dependent on
>>another variable 'color'; so for each color there is a 'target'. As I want to
>show only the target for the selected color, I use this transient variable. It
>is >used as well to set a new target (from the table view) for the selected
>color.> >In the model I have imposed a minimum, maximum and default value for
>'target', and the table column is set to validate immediately. This works
>correctly. >However, the feedback in the validation sheet is rather minimal.
>>So, first question: how can I change the validation message, to include e.g.
>required range etc.?> >Another thing is, I have found that I can erase the
>value in the table view, without a validation error getting triggered! A
>nil-value is not acceptable. The >easiest solution I've found is just to make
>it persistent (non-transient). But I think 'non-optional' should mean
>'required', meaning the value should never be >nil... especially since I gave
>a min, max and default value.>Is there a better way to do this while keeping
>the variable transient?>
> (Pay careful attention to what > it says about validation *instead of*
> versus validation *as well as* > Core Data's other validation mechanisms.)
Yes, I have found that I should not do it both. That is, if I check also in
code on maximum/minimum, an error message 'multiple validation errors' will
come up.
>There's also a way of localizing the built-in error messages, which >may be
>another solution to your first question if you just want to >vary the wording
>a bit:>>
>http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/Articles/cdUsingMOM.html#/
> /apple_ref/doc/uid/TP40005190-SW13
Well, that turns out to be complicated... I have to retrieve the validation
predicates for max, min from the model:
NSEntityDescription * recipeEntity = [NSEntityDescription entityForName:
@"Recipe" inManagedObjectContext: [[NSApp delegate] managedObjectContext]];
NSAttributeDescription * targetDescription = [[recipeEntity propertiesByName]
valueForKey: @"target"]; NSArray * validationPredicates = [targetDescription
validationPredicates];
after which the predicates need to be parsed in order to find which is the max
/ min predicate. Then, the custom error message has to be fed to the managed
object model's localizationDictionary, which I don't fully understand... The
following code does not work:
NSManagedObjectModel * model = [[NSApp delegate] managedObjectModel];
NSMutableDictionary * localizedDict = [NSMutableDictionary dictionary];
for (unsigned int i = 0; i < [validationPredicates count]; i++) {
NSComparisonPredicate * predicate = [validationPredicates objectAtIndex: i];
NSString * description = [predicate description]; double value = [[[predicate
rightExpression] constantValue] doubleValue]; if ( [description hasPrefix:
@"SELF >"] ) { minimumTarget = value; id validationWarning =
[[targetDescription validationWarnings] objectAtIndex: i]; [localizedDict
setValue: @"Test string 123" forKey: [NSString stringWithFormat:
@"ErrorString/%@", validationWarning]]; [model setLocalizationDictionary:
localizedDict]; }
}
Any ideas on how this can be done in a *simpler* way?
Thanks so far,
Arthur
> >Thanks in advance,>Arthur
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