Saving in NSDocumentDirectory uniquely - iphone

Question

Hi Im really having a hard time saving in my NSDocumentDirectory.Im using AGImagePickerby the way. Yes I was able to save this in NSDocumentDirectory. But how to save them uniquely ( in terms of their own then converting their names into oneSlotImages) or save them with their unique IDs then load them back. Sorry Im kinda new to this UIImagePickerControllerMediaURL thing., I think that would be my solution to my other problem for not overlaping them when saving. How to save this using their unique ID, or UIImagePickerControllerMediaURL.
for (int i = 0; i < info.count; i++) {
NSLog(#"%#", [info objectAtIndex:i]);
NSArray *paths = NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask ,YES );
NSString *documentsDir = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"oneSlotImages%d.png", i]];
ALAssetRepresentation *rep = [[info objectAtIndex: i] defaultRepresentation];
UIImage *image = [UIImage imageWithCGImage:[rep fullResolutionImage]];
//----resize the images
image = [self imageByScalingAndCroppingForSize:image toSize:CGSizeMake(256,256*image.size.height/image.size.width)];
NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:savedImagePath atomically:YES];
Thanks for the help. Much Appreciated.

Answer 1

You could always keep a list of used names and do something like this
int i = 1;
while([listOfUsedNames containsObject:nextAvailableTile]) {
nextAvailableTitle = [kDefaultImageName stringByAppendingFormat:#" %d", i];
i++;
}
// found an unused name

Answer 2

The URL for each image is unique right? So we can make use of this. Convert the URL into MD5 string (which form a unique identifier for each image). And save with that name (like "MD5string.png").
Why can't we use this?
Hope this helps you.
For converting to MD5, please create a file named NSString+MD5.h and put the code
#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonDigest.h>
#interface NSString(MD5)
- (NSString *)MD5;
#end
in it.
Then in the NSString+MD5.m,
#import "NSString+MD5.h"
#implementation NSString(MD5)
- (NSString*)MD5
{
const char *ptr = [self UTF8String];
unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];
CC_MD5(ptr, strlen(ptr), md5Buffer);
NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[output appendFormat:#"%02x",md5Buffer[i]];
return output;
}
#end
Import the NSString+MD5.h class where ever you want to use the MD5 function with normal NSString object.
In you code if you have the UIImagePickerControllerMediaURL string, since it is unique for every file you can convert in to MD5 String like
NSString *imgURL = [NSString stringWithString: UIImagePickerControllerMediaURL];
NSString *MD5String = [imgURL MD5];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"%#.png", MD5String]];
Use that path to save your image file.
On Loading,
Convert the UIImagePickerControllerMediaURL into MD5 and check in the Documents directory for the file
// In this the UIImagePickerControllerMediaURL is the URL of media file to load
NSString *imgURL = [NSString stringWithString: UIImagePickerControllerMediaURL];
NSString *MD5String = [imgURL MD5];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"%#.png", MD5String]];
Then do the checking with the fileExistsAtPath method of NSFileManager and if exists then load the file from the path. Thats it.
Note: For this you want to keep the UIImagePickerControllerMediaURL of the images you saved in documents directory locally somewhere in your app (In DB or NSUserDefaults) for make use of then at the time of loading.

Answer 3

Try this:
NSMutableString *imageName = [[[NSMutableString alloc] initWithCapacity:0] autorelease];
CFUUIDRef theUUID = CFUUIDCreate(kCFAllocatorDefault);
if (theUUID) {
[imageName appendString:NSMakeCollectable(CFUUIDCreateString(kCFAllocatorDefault, theUUID))];
CFRelease(theUUID);
}
[imageName appendString:#".png"];