objective-c example of detecting way points

DrawPane.m

//
//  A sample from DrawPane.m/h
//  Created by John Trengrove
//

#import <UIKit/UIKit.h>

@class Letter;
@class Dot;
@class AppDelegate;

@interface DrawPane : UIView {
    NSMutableArray *dots;
    UIBezierPath *bezier;
    Letter *letter;
    AppDelegate *appDelegate;
    Dot *prev1;
    Dot *prev2;
}

- (BOOL)goodDrawing;
- (void)clearDots;
- (void)initialise;
- (void)addStartDot:(CGPoint)location;
- (void)addDot:(CGPoint)location;

CGPoint midPoint(Dot *p1, Dot *p2);

@property(readwrite, nonatomic, retain) Letter *letter;
@property(nonatomic, retain) NSMutableArray *dots;
@property(nonatomic, retain) UIBezierPath *bezier;
@property(nonatomic,retain) AppDelegate *appDelegate;

@end

// ... snip ...

// goodDrawing matches an array of Strokes generated from a user
// against a set of Guide Points and determines if the Strokes
// satisfy the Guide Points.

- (BOOL)goodDrawing {
    
    int strokeIndex = 0;
    // User entered dots
    int dotIndex = 0;
    int guideDotIndex = 0;
    
    Stroke *currentStroke;
    Dot * guideDot;
    Dot * dot;
    
    // NSLog(@"Detected %d strokes", [self.letter.strokes count]);
    
    // Iterate through dot array and attempt to find match
    while (dotIndex < [self.dots count]) {
        
        // get the next guide dot
        if (strokeIndex < [self.letter.strokes count]) {
            currentStroke = [self.letter.strokes objectAtIndex:strokeIndex];
            if (guideDotIndex < [currentStroke.dots count]) {
                guideDot = [currentStroke.dots objectAtIndex:guideDotIndex];
                // NSLog(@"using guide dot x:%f y:%f",guideDot.x, guideDot.y);
            }
            // Move onto next stroke
            else {
                strokeIndex += 1;
                guideDotIndex = 0;
                // NSLog(@"Stroke index: %d", strokeIndex);
                continue;
            }
        }
        // Exit FAILURE
        else {
            return NO;
        }
        
        dot = [self.dots objectAtIndex:dotIndex];
        if ([guideDot contains:dot]) {
            // NSLog(@"Matched guide dot");
            guideDotIndex += 1;
            // Exit YES if all guide dots have been matched
            if (guideDotIndex == [currentStroke.dots count] && strokeIndex == [self.letter.strokes count]-1) {
                return YES;
            }
        }
        
        dotIndex += 1;
    }
    return NO;
}