管理应用程序的Documents目录中的文件和目录

Question

I am trying to work out how to manage files and directories in my app's Documents folder. I have been trying to make sense of the NSData class but without joy. I have managed to write an image to my Documents folder using the following code.

- (IBAction)writeImage:(id)sender
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:@"savedImage.png"];

UIImage *image = [UIImage imageNamed:@"Default.png"];
NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:savedImagePath atomically:NO];
}

What I would like to know is how to create and delete directories and files. Can anyone point me to correct place to look? Thanks in advance.

Answer 1

For folder you can use:

 [[NSFileManager defaultManager] createDirectoryAtURL:folder withIntermediateDirectories:YES attributes:nil error:&error];

It will create all folders at given path which is cool :)

Answer 2

The NSFileManager class enables you to perform many generic file-system operations and insulates an app from the underlying file system.

There is a class method in NSFileManager class called +defaultManager which always gives you same FileManager object or shared Object and most file operations can be performed using this shared file manager object.

Answer 3

You can write by avoiding overwriting your file if it already exists as below and can also check if the folder is writable or not.

NSString *imageName = @"Default.png";
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [paths objectAtIndex:0];
NSString *savedImagePath = [NSString stringWithFormat:@"%@/%@", documentsDirectoryPath, imageName];

// Write only if file does not exist.
if (![[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]) {
    NSData *imageData = UIImagePNGRepresentation(image);
    [imageData writeToFile:savedImagePath atomically:NO];
}


// Check if folder is writable
NSString *folderPath = @"someFolderPath";
if ([[NSFileManager defaultManager] isWritableFileAtPath:folderPath]) {
    NSLog(@"Folder is writable");
}else {
    NSLog(@"Folder is not writable");
}