I’ll say right off I am an inexperienced Cocoa programmer, and I apologize if my question is answered in the docs somehow and I merely missed it, or there was something I don’t understand in how the NSPredicateEditor works. However, I did attempt to search in the docs and googled, to little effect. Thus, I bring the question to you.
I am attempting to filter a Core Data-based table view with an NSPredicateEditor. The filtering works fine, in terms of the rows filtering based on various criteria, through creating an NSCompoundPredicate. However, when a row in the Predicate Editor has no text in its search field, the NSPredicate that is returned is something along the lines of
dataName CONTAINS[cd] ""
…which matches none of the Core Data records — not what I want. If that search field in that row is blank, essentially I don’t want it to filter my data set at all.
My question then is, what is the easiest/best solution to ignore these parts of the predicate? My initial idea was to parse the NSPredicateEditor value row-by-row with (NSPredicate *)predicateForRow:(NSInteger)row and rebuild the predicate myself, ignoring lines which are trying to match "", but that seems unnecessarily cumbersome. Taking the final NSCompoundPredicate apart with - (NSArray *)subpredicates and editing it that way also seems like perhaps I’m taking the wrong tack. Is there a more elegant way to do this?
*To be clear, I’m thinking of editing the copy of the predicate which I then pass to the controller for my table view, not actually editing the initial predicate that is currently stored in the NSPredicateEditor.
It looks like you should be able to subclass NSPredicateEditor and override
predicateForRow:(declared in NSPredicateEditor’s superclass, NSRuleEditor) and do your substitution there. You would basically just called super’s implementation, then examine the predicate and return a newly created one if necessary.