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copied!<p>Personally, I'd be inclined to do it as follows:</p> <ol> <li><p>First, I'd be inclined to save the C array of <code>CLLocationCoordinate2D</code> coordinates that I pass to <code>MKPolygon</code> instance method <code>polygonWithCoordinates</code> (rather than a <code>MKMapPoint</code> C array). You can adapt this code if you'd rather use <code>MKMapPoints</code>, but I prefer a format which I can examine externally and make sense of (namely the latitude and longitude values of <code>CLLocationCoordinate2D</code>). So, let's assume that you make your <code>MKPolygon</code> with a line of code like so:</p> <pre><code>MKPolygon* poly = [MKPolygon polygonWithCoordinates:coordinates count:count]; </code></pre> <p>You could, therefore save the coordinates like so:</p> <pre><code>[self writeCoordinates:coordinates count:count file:filename]; </code></pre> <p>Where <code>writeCoordinates:count:filename:</code> is defined as follows:</p> <pre><code>- (void)writeCoordinates:(CLLocationCoordinate2D *)coordinates count:(NSUInteger)count file:(NSString *)filename { NSData *data = [NSData dataWithBytes:coordinates length:count * sizeof(CLLocationCoordinate2D)]; [data writeToFile:filename atomically:NO]; } </code></pre> <p>You could then make the <code>MKPolygon</code> from the file with:</p> <pre><code>MKPolygon* poly = [self polygonWithContentsOfFile:filename]; </code></pre> <p>where <code>polygonWithContentsOfFile</code> is defined as:</p> <pre><code>- (MKPolygon *)polygonWithContentsOfFile:(NSString *)filename { NSData *data = [NSData dataWithContentsOfFile:filename]; NSUInteger count = data.length / sizeof(CLLocationCoordinate2D); CLLocationCoordinate2D *coordinates = (CLLocationCoordinate2D *)data.bytes; return [MKPolygon polygonWithCoordinates:coordinates count:count]; } </code></pre></li> <li><p>Alternatively, you could read and write the array of <code>CLLocationCoordinate2D</code> in a plist format (which renders it in a human readable format), by replacing the two above methods with:</p> <pre><code>const NSString *kLatitudeKey = @"latitude"; const NSString *kLongitudeKey = @"longitude"; - (void)writeCoordinates:(CLLocationCoordinate2D *)coordinates count:(NSUInteger)count file:(NSString *)filename { NSMutableArray *array = [NSMutableArray arrayWithCapacity:count]; for (NSUInteger i = 0; i < count; i++) { CLLocationCoordinate2D coordinate = coordinates[i]; [array addObject:@{kLatitudeKey:@(coordinate.latitude), kLongitudeKey:@(coordinate.longitude)}]; } [array writeToFile:filename atomically:NO]; } - (MKPolygon *)polygonWithContentsOfFile:(NSString *)filename { NSArray *array = [NSArray arrayWithContentsOfFile:filename]; NSUInteger count = [array count]; CLLocationCoordinate2D coordinates[count]; for (NSUInteger i = 0; i < count; i++) { NSDictionary *dictionary = array[i]; coordinates[i].latitude = [dictionary[kLatitudeKey] doubleValue]; coordinates[i].longitude = [dictionary[kLongitudeKey] doubleValue]; } return [MKPolygon polygonWithCoordinates:coordinates count:count]; } </code></pre></li> </ol> <p>Clearly you'd want to add error checking code to make sure that the <code>writeToFile</code> and the <code>dataWithContentsOfFile</code> (or <code>arrayWithContentsOfFile</code>) succeeded, but hopefully this gives you the idea.</p>

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