iPhone使用唯一密钥加载并保存多个UIImages？

Question

我知道有一些解决方案用于在iPhone上保存和加载图像。然而，没有人为我工作。

例如，下面的链接有大的代码块，它可以让您加载和保存一个UIImage了一个独特的密钥，但我不能工作了如何加载使用此代码的图像时告诉我们，如果根据该图像密钥已经存在或没有。

http://www.friendlydeveloper.com/2010/02/using-nsfilemanager-to-save-an-image-to-or-loadremove-an-image-from-documents-directory-coding/

//saving an image 
- (void)saveImage:(UIImage*)image:(NSString*)imageName { 
    NSData *imageData = UIImagePNGRepresentation(image); //convert image into .png format. 
    NSFileManager *fileManager = [NSFileManager defaultManager];//create instance of NSFileManager 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); //create an array and store result of our search for the documents directory in it 
    NSString *documentsDirectory = [paths objectAtIndex:0]; //create NSString object, that holds our exact path to the documents directory 
    NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", imageName]]; //add our image to the path 
    [fileManager createFileAtPath:fullPath contents:imageData attributes:nil]; //finally save the path (image) 
    NSLog(@"image saved"); 
} 

//removing an image 
- (void)removeImage:(NSString*)fileName { 
    NSFileManager *fileManager = [NSFileManager defaultManager]; 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", fileName]]; 
    [fileManager removeItemAtPath: fullPath error:NULL]; 
    NSLog(@"image removed"); 
} 

//loading an image 
- (UIImage*)loadImage:(NSString*)imageName { 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", imageName]]; 
    return [UIImage imageWithContentsOfFile:fullPath]; 
} 

如果你能帮助我制定出了这将是非常赞赏。我需要保存多个图像，并根据给定键是否已存在来加载它们。

Answer 1

如果你想获得具有唯一键的图像，请尝试使用UUID。这与这里独特的key..For例子永远作罢图像是使用UUID的例子..

- (NSString *)pathForImageFileWithPrefix:(NSString *)Prefix 
{ 
    CFUUIDRef uuid; 
    CFStringRef uuidStr; 
    uuid = CFUUIDCreate(NULL); 
    uuidStr = CFUUIDCreateString(NULL, uuid); 
    NSData *imageData = UIImageJPEGRepresentation(chosenImage, 1.0); 
    NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString* documentsDirectory = [paths objectAtIndex:0]; 
    result = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@_%@.png",Prefix, uuidStr]]; 
    [imageData writeToFile:result atomically:NO]; 
    CFRelease(uuidStr); 
    CFRelease(uuid); 
    return result; 
} 

Answer 2

如果我得到你的问题吧，你想知道与给定图像文件名的文件是否已经存在？那么你可以只使用

bool fileExists = [NSFileManager defaultManager] fileExistsAtPath:filePath];