PredicateOptimiser

PredicateOptimiser is all about doing cool things with NSPredicate objects. There are two classes:

• POPredicateOptimiser This class can be used to optimise your NSPredicate object.
• POPredicateFormatter This class can be used to format your NSPredicate object.

POPredicateOptimiser

POPredicateOptimiser has a single method optimisedPredicateForPredicate:. Passing it an NSPredicate object will return you a new (possibly optmised) NSPredicate object in accordance property optimisationType.

optimisationType takes one of the following values:

• POPredicateOptimisationTypeNone The optimiser will simply return a copy of the NSPredicate object.
• POPredicateOptimisationTypeBest The optimiser will do its best to optimise the NSPredicate object.

For example:

Before	After
not (a > b)	a <= b
... OR TRUEPREDICATE OR ...	TRUEPREDICATE
... AND FALSEPREDICATE AND ...	FALSEPREDICATE

POPredicateFormatter

POPredicateFormatter has a single method stringFromPredicate:. Passing it an NSPredicate object will return you an NSString in accordance with the property displayType.

displayType takes one of the following values:

• POPredicateDisplayTypeString The formatter will simply return the result of calling description on the NSPredicate object.
• POPredicateDisplayTypeCocoa The formatter will return an NSString containing the code neccessary to reproduce the NSPredicate object in code.

For example, string contains[cd] 'Foo' would produce:

[NSComparisonPredicate predicateWithLeftExpression:[NSExpression expressionWithFormat:@"string" /* NSKeyPathExpression */rightExpression:[NSExpression expressionWithFormat:@""Foo"" /* NSConstantValueExpression */ modifier:NSDirectPredicateModifier type:NSContainsPredicateOperatorType options:NSCaseInsensitivePredicateOption | NSDiacriticInsensitivePredicateOption]

License

The license for the code is included with this project; it's basically a BSD license with attribution.

John Scott http://jjrscott.com/