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Suppose I have an NSURL that points to my NSDocumentationDirectory but the NSURL has an unknown number of subdirectories in it. When writing to the URL, will have I have to check for existence of the directories along the path and create them if they don't exist, or can I just write to the NSURL? If the former, how do I do it?

Here's what I've tried so far, and it's not working. I assume it's because the subdirectories along the path don't exist.

NSData *imageData;
if (imageURL) {
   //imageURL points to an image on the internet.
   NSLog(@"Path components\n%@",[imageURL pathComponents]);
   NSFileManager *fileManager = [[NSFileManager alloc] init];
   NSArray *urls = [fileManager URLsForDirectory:NSDocumentationDirectory inDomains:NSUserDomainMask];
   //Sample of urls[0]: file://localhost/var/mobile/Applications/blahblah/Library/Documentation/
   NSURL *cachedURL = urls[0]; //iOS, so this will be the only entry.
   //Manually add a cache directory name.
   cachedURL = [cachedURL URLByAppendingPathComponent:@"cache"];
   NSArray *passedPathComponents = [imageURL pathComponents];
   for (NSString *pathComponent in passedPathComponents) {
      cachedURL = [cachedURL URLByAppendingPathComponent:pathComponent];
      NSLog(@"Added component %@ making URL:\n%@",pathComponent,cachedURL);
   }
   // Check if image data is cached.
   // If cached, load data from cache.
   imageData = [[NSData alloc] initWithContentsOfURL:cachedURL];
   if (imageData) {
      //Cached image data found
      NSLog(@"Found image data from URL %@",cachedURL);
   } else  {
      // Did not find the image in cache. Retrieve it and store it.
      // Else (not cached), load data from passed imageURL.
      //     Update cache with new data.
      imageData = [[NSData alloc] initWithContentsOfURL:imageURL];
      if (imageData) {
         // Write the imageData to cache
         [imageData writeToURL:cachedURL atomically:YES]; //This is the line I'm asking about
      }
   }
   NSLog(@"Value of urls is %@",urls[0]);
}

I am not interested in caching APIs I can tap into. The purpose of this question is to understand how to properly use NSFileManager.

Edit: I'm thinking maybe I need to use createDirectoryAtURL:withIntermediateDirectories:attributes:error: on the path excluding the last component.

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1 Answer 1

up vote 0 down vote

I got it to work using createDirectoryAtURL:... as follows:

  for (NSString *pathComponent in passedPathComponents) {
     if ([pathComponent isEqualToString:lastComponent]) {
        //Now we're looking at the file name. Ensure the directory exists. What we have so far is the directory.
        if ([fileManager createDirectoryAtURL:cachedURL withIntermediateDirectories:YES attributes:nil error:NULL]) {
           //NSLog(@"Directory was created or already exists");
        } else {
           NSLog(@"Error creating directory %@",[cachedURL description]);
        };
     }
     cachedURL = [cachedURL URLByAppendingPathComponent:pathComponent];
  }
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