Quickies for NSFIleManager

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General

• Finding things like user's Document directory. [permalink]
  NSFileManager's URLForDirectory is how you can find the location of things like the user's Documents directory. The domain is what domain, like NSDocumentDirectory, NSUserDomainMask will give you the URL to the iOS sandbox for your app's user files. appropriateForURL is is advanced - mainly of use if you're going to be doing an atomic swap of files.

  In Swift 4:

          let fm = FileManager()
          do {
              let documentDirectoryURL = try fm.url(for: .documentDirectory, 
                                                    in: .userDomainMask, 
                                                    appropriateFor: nil, 
                                                    create: true)
              // use documentDirectoryURL
          } catch {
              // handle error as you see fit
          }
  

  ObjC:

      NSFileManager *fm = [NSFileManager defaultManager];
      NSError *error;
  
      NSURL *localDocumentDirectory =
          [fm URLForDirectory: NSDocumentDirectory
              inDomain: NSUserDomainMask
              appropriateForURL: nil
              create: YES
              error: &error];
  
      if (localDocumentDirectory == nil) {  // never compare error == nil
          NSLog (@"could not url for directory, dude - %@", error);
      }
  

  (looking how to do it with paths? )

• Getting directory listing based on URL [permalink]
  

      NSURL *mediaDirectory = ...;
  
      NSArray *contents = [fm contentsOfDirectoryAtURL: mediaDirectory
                              includingPropertiesForKeys: @[]
                              options: 0
                              error: &error];
  
      if (contents == nil) {
          NSLog (@"could not contents of %@ - %@", mediaDirectory, error);
          return nil;
      }
  

  There's also enumeratorAtURL:includingPropertiesForKeys:... that gives you back a directory enumerator.

• Moving a file to a tilde file [permalink]
  

      NSString *filename = @"/my/original/file/name";
      NSString *tildeFilename;
      tildeFilename = [NSString stringWithFormat: @"%@~", filename];
  
      // remove it first, otherwise the move will fail
      [defaultManager removeFileAtPath: tildeFilename
                      handler: nil];
  
      // now rename the file
      [defaultManager movePath: filename
                      toPath: tildeFilename
                      handler: nil];

  If you want to stick the tidle before the file extension (so the finder could open ook~.tiff), try this:

  	NSString *pathExtension = [filename pathExtension];
  	if (!pathExtension) {
  		tildeFilename = [filename stringByAppendingString: @"~"];
  	} else {
  		tildeFilename = [NSString stringWithFormat: @"%@~.%@", [filename stringByDeletingPathExtension], pathExtension];
  	}

  (Thanks to Peter Hosey for this one)

• Removing a file [permalink]
  

      NSFileManager *defaultManager;
      defaultManager = [NSFileManager defaultManager];
  
      [defaultManager removeFileAtPath: tildeFilename
                      handler: nil];

  The handler is an object that will be sent message, like fileManager:shouldProceedAfterError: if something goes wrong during the removal.

• Saving an NSData to a file [permalink]
  

      NSString *filename = @"/this/is/my/file/name";
      NSData *data = // get NSData from somewhere, like NSPropertyListSerialization
  
     [data writeToFile: filename  atomically: NO];

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