I don't think it's possible without a format string. "$x.firstName" gets turned into an expression of type NSFunctionExpression. The operator is a variable expression, and the first argument is an expression with a private type (10). gdb shows that the class of that argument is "NSKeyPathSpecifierExpression", but there doesn't appear to be a way to create one programmatically without a format string.
Similarly, the SUBQUERY(...).@count gets turned into a FUNCTION() expression. The operand is the subquery expression, and the first argument is another expression of type 10. I think you're out of luck and will have to build a format string and pass that to predicateWithFormat:. I'd probably file a bug requesting more API if I were you. HTH, Dave On Sep 26, 2011, at 7:05 AM, Willeke wrote: > hi, > > How do I programmatically create the $x.firstname and .@count parts of this > expression? > SUBQUERY(residents, $x, $x.firstname == "Jane" && $x.lastname == "Doe").@count > > When I create a subquery predicate with predicateWithFormat:, the class of > the $x.firstname and .@count expressions is NSKeyPathExpression and the type > is NSFunctionExpressionType. The operand is an expression of type > NSVariableExpressionType or NSSubqueryExpressionType. The function is > valueForKeyPath:. > > When I create an expression with expressionForKeyPath:, the operand is SELF > instead of the variable or the subquery. When I create an expression with > expressionForFunction:selectorName:arguments:, the class is > NSFunctionExpression. When the argument is a keypath expression, instead of > $x.firstname the expression tries to evaluate $x.Jane and that doesn't work. > executeFetchRequest throws an exception: -constantValue only defined for > abstract class. Define -[NSKeyPathExpression constantValue]! > If the argument is a constant value expression, executeFetchRequest throws an > exception: -keyPath only defined for abstract class. Define > -[NSConstantValueExpression keyPath]!. > > The predicate will be edited in a rule editor so I have to convert it to > criteria and back. > The predicate will be used as filter predicate of an array controller in > entity mode and/or in a fetch request with Core Data (SQLite). > > Thanks, > Willeke _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
