Python for Bioinformatics: NSPredicate: compound Cocoa example in code

Saturday, March 12, 2011

NSPredicate: compound Cocoa example in code

I'm resisting the temptation to call this simple---it's not! All we're doing is filtering an array of dicts for those whose 'value' is neither too large nor too small. I have no idea why it has to be this complicated. The example is from the NSPredicate docs (as reformatted and with renamed vars by me):

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    NSArray *A = [NSArray arrayWithObjects:
        [NSDictionary dictionaryWithObject:[
            NSNumber numberWithInt:5] forKey:@"value"],
        [NSDictionary dictionaryWithObject:[
            NSNumber numberWithInt:50] forKey:@"value"], 
        [NSDictionary dictionaryWithObject:[
            NSNumber numberWithInt:500] forKey:@"value"], 
        nil];

    NSExpression *lhs = [NSExpression 
        expressionForKeyPath:@"value"];
    NSExpression *gtrhs = [NSExpression 
        expressionForConstantValue:[NSNumber numberWithInt:10]];
    NSExpression *ltrhs = [NSExpression 
        expressionForConstantValue:[NSNumber numberWithInt:100]];
    
    NSPredicate *gtpred;
    gtpred = [NSComparisonPredicate 
        predicateWithLeftExpression:lhs
                    rightExpression:gtrhs 
                           modifier:NSDirectPredicateModifier 
                               type:NSGreaterThanOrEqualToPredicateOperatorType 
                            options:0];
    
    NSPredicate *ltpred;
    ltpred = [NSComparisonPredicate 
        predicateWithLeftExpression:lhs
                    rightExpression:ltrhs 
                           modifier:NSDirectPredicateModifier 
                               type:NSLessThanOrEqualToPredicateOperatorType 
                            options:0];
                                                                                
    NSPredicate *pred;
    pred = [NSCompoundPredicate andPredicateWithSubpredicates:
                [NSArray arrayWithObjects:gtpred, ltpred, nil] ];
                
    NSArray *fA = [A filteredArrayUsingPredicate:pred];
    for (id obj in fA) {
        NSLog(@"%@", [obj description]);
    }
    return 0;
}

> gcc -o test pred.m -framework Foundation
> ./test
2011-03-12 11:48:31.640 test[70403:903] {
    value = 50;
}