Added new category on NSPredicate.

Author: jerrykrinock

NSPredicate+SSYPreflight.h

@@ -0,0 +1,20 @@
+#import <Foundation/Foundation.h>
+
+/*!
+ @brief    Returns whether or not the receiver can be used without raising
+ an exception
+ 
+ @details  If the user sets a row in NSPredicateEditor to the "matches"
+ predicate type and fills in an invalid regular expression pattern such as this
+ one:
+   (*(
+ the predicate returned by -[NSPredicateRuleEditor objectValue] be an invalid
+ and an exception will be raised if such a predicate is passed to, for example,
+ -[NSArrayController setFilterPredicate:], an exception will be raised :(
+ 
+ This method preflights such a predicate so you can avoid such an exception. */
+@interface NSPredicate (SSYValidate)
+
+- (BOOL)preflightValidate ;
+
+@end

NSPredicate+SSYPreflight.m

@@ -0,0 +1,45 @@
+#import "NSPredicate+SSYPreflight.h"
+
+@implementation NSPredicate (SSYValidate)
+
+- (BOOL)preflightValidate {
+    BOOL answer = YES ;
+    if ([self isKindOfClass:[NSComparisonPredicate class]]) {
+        if ([(NSComparisonPredicate*)self predicateOperatorType] == NSMatchesPredicateOperatorType) {
+            NSExpression* expression = [(NSComparisonPredicate*)self rightExpression] ;
+            if ([expression expressionType] == NSConstantValueExpressionType) {
+                id constantValue = [expression constantValue] ;
+                if ([constantValue isKindOfClass:[NSString class]]) {
+                    NSError* error = nil ;
+                    NSRegularExpression* regex = [[NSRegularExpression alloc] initWithPattern:constantValue
+                                                                                      options:0
+                                                                                        error:&error] ;
+                    /* The error returned does not usually give much
+                     additional information.  Here is an example:
+                     Error Domain=NSCocoaErrorDomain Code=2048 "The value “(*(” is invalid." UserInfo={NSInvalidValue=(*(}
+                     So, we don't bother passing it up. */
+                    if (!regex || (error != nil)) {
+                        answer = NO ;
+                    }
+                    [regex release] ;
+                }
+            }
+        }
+    }
+    else if ([self respondsToSelector:@selector(subpredicates)]) {
+        for (NSPredicate* predicate in [(NSCompoundPredicate*)self subpredicates]) {
+            if (![predicate preflightValidate]) {
+                answer = NO ;
+                break ;
+            }
+        }
+    }
+    else {
+        /*SSYDBL*/ NSLog(@"Whoooops: %@", [self className]) ;
+        /* Could be something like NSTruePredicate */
+    }
+    
+    return answer ;
+}
+
+@end