保存图像到一个目录

Question

嗨我想保存图像到一个目录，我通过NSData并做我认为将文件保存在我创建的目录中，但问题是，它不保存。这是我迄今为止所拥有的。为什么没有initWithContentsOfURL：encoding：error：work，它会返回null，但我使用的另一种方法是有效的？主要问题是WRITETOURL返回0，我认为这意味着信息没有正确存储，任何提示？

NSFileManager *fm = [[NSFileManager alloc] init]; 
    NSArray * directoryPaths = [fm URLsForDirectory:NSCachesDirectory inDomains:NSUserDomainMask]; 
    NSLog(@"%@", directoryPaths); 
    NSURL* dirPath = nil;  
    dirPath = [[directoryPaths objectAtIndex:0] URLByAppendingPathComponent:[NSString stringWithFormat:@"photos.jpeg"]]; 
    NSError* theError = nil; 
    [fm createDirectoryAtURL:dirPath withIntermediateDirectories:YES attributes:nil error:&theError]; 

UIImage* photoToStore = [UIImage imageWithData:photoToSave]; 

NSString *pathContainingPhoto = [[NSString alloc] initWithFormat:@"%@.jpeg", UIImageJPEGRepresentation(photoToStore, 1.0)]; 
NSError *error = nil; 


BOOL OK = [pathContainingPhoto writeToURL:dirPath atomically:YES encoding:NSUTF8StringEncoding error:&error]; 

NSLog(@"OK = %d", OK); //Returns 0 
NSLog(@"%@", dirPath); 

//WHY DOESNT THIS VERSION WORK? 
// NSString *pathToFile = [[NSString alloc] initWithContentsOfURL:dirPath encoding:NSUTF8StringEncoding error:&error]; 
NSLog(@"%@", pathToFile); 

    NSString* pathToFile = [NSString stringWithContentsOfURL:dirPath encoding:nil error:nil]; 
NSArray *dirContents = [fm contentsOfDirectoryAtPath:pathToFile error:nil]; 
NSLog(@"%@", dirContents); 

Answer 1

像这样和int在.h文件中计数并设置其初始值count = 0; in viewDidLoad：

NSString *stringPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)objectAtIndex:0]stringByAppendingPathComponent:[NSString stringWithFormat:@"Image_%d.png",count]; 
error = nil; 
if (![[NSFileManager defaultManager] fileExistsAtPath:stringPath]) // removing item it already exuts 
{ 
    [[NSFileManager defaultManager] removeItemAtPath:stringPath error:&error]; 
} 

if(photoToSave) // nsdata of image that u have 
{ 
    [photoToSave writeToFile:stringPath atomically:YES]; 
} 
count++; // maintaining count of images