A thin object wrapper around CGPath, mainly for the purpose of serializing paths. (Not yet converted to ARC, sorry.)

MWCGPath.h

//
//  MWCGPath.h
//
//  Created by Martin Winter on 14.01.11.
//  Copyright 2011 Martin Winter. All rights reserved.
//
//  Provides an NSObject wrapper around CGPathRef.
//

#if TARGET_OS_IPHONE
#import <UIKit/UIKit.h>
#import <CoreGraphics/CoreGraphics.h>
#else
#import <Cocoa/Cocoa.h>
#import <ApplicationServices/ApplicationServices.h>
#endif


@interface MWCGPath : NSObject

@property (nonatomic, retain) __attribute__((NSObject)) CGPathRef CGPath;

- (id)initWithCGPath:(CGPathRef)inCGPath;

@end

MWCGPath.m

//
//  MWCGPath.m
//
//  Created by Martin Winter on 14.01.11.
//  Copyright 2011 Martin Winter. All rights reserved.
//

#import "MWCGPath.h"


void MWCGPathApplierFunction(void *info, const CGPathElement *element)
{
    NSMutableArray *array = (NSMutableArray *)info;
    CGPathElementType type = element->type;
    CGPoint *points = element->points;
    
    // Determine number of points for element type.
    NSUInteger pointCount = 0;
    switch (type)
    {
        case kCGPathElementMoveToPoint:
            pointCount = 1;
            break;
            
        case kCGPathElementAddLineToPoint:
            pointCount = 1;
            break;
            
        case kCGPathElementAddQuadCurveToPoint:
            pointCount = 2;
            break;
            
        case kCGPathElementAddCurveToPoint:
            pointCount = 3;
            break;
            
        case kCGPathElementCloseSubpath:
            pointCount = 0;
            break;
            
        default:
            [array replaceObjectAtIndex:0 withObject:[NSNumber numberWithBool:NO]]; // Set status flag ...
            return; // ... and return.
    }
    
    // Serialize points.
    NSData *pointsData = [NSData dataWithBytes:points 
                                        length:(pointCount * sizeof(CGPoint))];
    
    // Package type and points.
    NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:type], @"type", 
                                pointsData, @"points", 
                                nil];
    
    // Add dictionary to array.
    [array addObject:dictionary];
}


// Return value is autoreleased.
NSData *MWNSDataFromCGPath(CGPathRef path)
{
    if (path == NULL) return nil;
    
    // Create array that will hold path elements. Initialize with status flag.
    NSMutableArray *array = [NSMutableArray arrayWithObject:[NSNumber numberWithBool:YES]];
    
    // Examine path elements.
    CGPathApply(path, array, MWCGPathApplierFunction);
    
    // Serialize array.
    return [NSKeyedArchiver archivedDataWithRootObject:array];
}


 // Caller is responsible for releasing return value.
CGPathRef MWCGPathCreateFromNSData(NSData *data)
{
    if (data == nil) return NULL;
    
    // Unserialize array.
    NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithData:data];
    
    // Recreate path.
    CGMutablePathRef path = CGPathCreateMutable();
    for (NSUInteger elementIndex = 0; elementIndex < [array count]; elementIndex++)
    {
        NSDictionary *dictionary = [array objectAtIndex:elementIndex];
        CGPathElementType type = [(NSNumber *)[dictionary objectForKey:@"type"] intValue];
        CGPoint *points = (CGPoint *)[(NSData *)[dictionary objectForKey:@"points"] bytes];
        
        switch (type)
        {
            case kCGPathElementMoveToPoint:
                CGPathMoveToPoint(path, NULL, points[0].x, points[0].y);
                break;
                
            case kCGPathElementAddLineToPoint:
                CGPathAddLineToPoint(path, NULL, points[0].x, points[0].y);
                break;
                
            case kCGPathElementAddQuadCurveToPoint:
                CGPathAddQuadCurveToPoint(path, NULL, points[0].x, points[0].y, points[1].x, points[1].y);
                break;
                
            case kCGPathElementAddCurveToPoint:
                CGPathAddCurveToPoint(path, NULL, points[0].x, points[0].y, points[1].x, points[1].y, points[2].x, points[2].y);
                break;
                
            case kCGPathElementCloseSubpath:
                CGPathCloseSubpath(path);
                break;
                
            default:
                CGPathRelease(path);
                return NULL;
        }
    }
    
    return path;
}


@implementation MWCGPath

@synthesize CGPath;


- (id)initWithCGPath:(CGPathRef)inCGPath
{
    self = [super init];
    if (self)
    {
        if (inCGPath != NULL)
        {
            CGPath = CGPathCreateCopy(inCGPath);
        }
    }
    return self;
}


- (id)init
{
    return [self initWithCGPath:NULL];
}


- (void)dealloc
{
    if (CGPath != NULL) CGPathRelease(CGPath);
    [super dealloc];
}


#pragma mark - NSCoding Protocol.


- (id)initWithCoder:(NSCoder *)decoder
{
    self = [super init];
    if (self)
    {
        NSData *CGPathData = [decoder decodeObjectForKey:@"CGPathData"];
        CGPath = MWCGPathCreateFromNSData(CGPathData); // Retain count 1.
    }
    return self;
}


- (void)encodeWithCoder:(NSCoder *)encoder
{
    NSData *CGPathData = MWNSDataFromCGPath(CGPath);
    [encoder encodeObject:CGPathData forKey:@"CGPathData"];
}


@end