Category on NSBezierPath to approximate the length of a curve

NSBezierPath+Length.h

//
//  NSBezierPath+Length.h
//
//  Created by mcianni on 10/14/12.
//

#import <Cocoa/Cocoa.h>

@interface NSBezierPath (Length)
- (double)length;
@end

@implementation NSBezierPath (Length)

- (double)length
{
    NSBezierPath *flattened_path = [self bezierPathByFlatteningPath];
    int segments = (int)flattened_path.elementCount;
    NSPoint last_point;
    NSPoint point;
    double length;
    
    for (int i=0; i<segments; i++) {
        /*
         * Normally, elementAtIndex:associatedPoints: would set the variable 
         * passed to associatedPoints as an array of NSPoints with max 
         * size 3. However, since we've called bezierPathByFlatteningPath, 
         * we can assume we'll always get a single point. The other points 
         * are normally used as control points for bezier curves.
         */
        NSBezierPathElement e = [flattened_path elementAtIndex:i
                                              associatedPoints:&point];
        
        // e == 0 is a moveToPoint command
        if (e == 0) {
            last_point = point;
        }
        else {
            // distance formula
            double distance = sqrt(pow(point.x - last_point.x, 2) +
                                   pow(point.y - last_point.y, 2));
            length += distance;
            last_point = point;
        }
        
    }
    return length;
}
@end