Python for Bioinformatics: Cocoa: strip for NSString

Thursday, September 24, 2009

Cocoa: strip for NSString

A few weeks ago I was complaining that NSString doesn't have a strip method like I use all the time in Python. I was wrong. It's called stringByTrimmingCharactersInSet:. Here is a bit of code (run from the command line) that exercises three useful NSString functions:

• componentsSeparatedByString
• componentsSeparatedByCharactersInSet
• stringByTrimmingCharactersInSet

// gcc -o strings stringstuff.m -framework Foundation
// ./strings
#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    NSString *s = [[NSString alloc] initWithString:@"v\nx y;z"];
    NSArray *a = [s componentsSeparatedByString:@"\n"];
    NSLog(@"a = %@", [a description]);
    
    NSCharacterSet *cs = 
        [NSCharacterSet characterSetWithCharactersInString:@"\n ;"];
    a = [s componentsSeparatedByCharactersInSet:cs];
    NSLog(@"a = %@", [a description]);

    NSString *s2 = [[NSString alloc] initWithString:@"   x y z   "];
    cs = [NSCharacterSet 
        characterSetWithCharactersInString:@" "];
    NSString *s3 = [s2 stringByTrimmingCharactersInSet:cs];
    NSLog(@"s3 = %@, length %u", [s3 description], [s3 length]);

    [s release];
    [s2 release];
    [pool drain];
    return 0;
}

Here is the output:

.. $ ./strings
.. s = v
x y;z
.. a = (
    v,
    "x y;z"
)
.. a = (
    v,
    x,
    y,
    z
)
.. s3 = x y z, length 5