Instance Method

enumeratorAtURL:includingPropertiesForKeys:options:errorHandler:

Returns a directory enumerator object that can be used to perform a deep enumeration of the directory at the specified URL.

Declaration

- (NSDirectoryEnumerator<NSURL *> *)enumeratorAtURL:(NSURL *)url includingPropertiesForKeys:(NSArray<NSURLResourceKey> *)keys options:(NSDirectoryEnumerationOptions)mask errorHandler:(BOOL (^)(NSURL *url, NSError *error))handler;

Parameters

url

The location of the directory for which you want an enumeration. This URL must not be a symbolic link that points to the desired directory. You can use the URLByResolvingSymlinksInPath method to resolve any symlinks in the URL.

keys

An array of keys that identify the properties that you want pre-fetched for each item in the enumeration. The values for these keys are cached in the corresponding NSURL objects. You may specify nil for this parameter. For a list of keys you can specify, see NSURLResourceKey.

mask

Options for the enumeration. For a list of valid options, see NSDirectoryEnumerationOptions.

handler

An optional error handler block for the file manager to call when an error occurs. The handler block should return YES if you want the enumeration to continue or NO if you want the enumeration to stop. The block takes the following parameters:

url

An NSURL object that identifies the item for which the error occurred.

error

An NSError object that contains information about the error.

If you specify nil for this parameter, the enumerator object continues to enumerator items as if you had specified a block that returned YES.

Return Value

An NSDirectoryEnumerator object that enumerates the contents of the directory at url. If url is a filename, the method returns an enumerator object that enumerates no files—the first call to nextObject returns nil.

Discussion

Because the enumeration is deep—that is, it lists the contents of all subdirectories—this enumerator object is useful for performing actions that involve large file-system subtrees. If the method is passed a directory on which another file system is mounted (a mount point), it traverses the mount point. This method does not resolve symbolic links or mount points encountered in the enumeration process, nor does it recurse through them if they point to a directory.

For example, if you pass a URL that points to /Volumes/MyMountedFileSystem, the returned enumerator will include the entire directory structure for the file system mounted at that location. If, on the other hand, you pass /Volumes, the returned enumerator will include /Volumes/MyMountedFileSystem as one of its results, but will not traverse into the file system mounted there.

The NSDirectoryEnumerator class has methods for skipping descendants of the existing path and for returning the number of levels deep the current object is in the directory hierarchy being enumerated (where the directory passed to enumeratorAtURL:includingPropertiesForKeys:options:errorHandler: is considered to be level 0).

This code fragment enumerates a URL and its subdirectories, collecting the URLs of files (skips directories). It also demonstrates how to ignore the contents of specified directories, in this case directories named “_extras”.

NSURL *directoryURL = [[NSBundle mainBundle] bundleURL];
NSFileManager *localFileManager= [[NSFileManager alloc] init];
NSDirectoryEnumerator *directoryEnumerator =
   [localFileManager enumeratorAtURL:directoryURL
          includingPropertiesForKeys:@[NSURLNameKey, NSURLIsDirectoryKey]
                             options:NSDirectoryEnumerationSkipsHiddenFiles
                        errorHandler:nil];
 
NSMutableArray<NSURL *> *mutableFileURLs = [NSMutableArray array];
for (NSURL *fileURL in directoryEnumerator) {
    NSNumber *isDirectory = nil;
    [fileURL getResourceValue:&isDirectory forKey:NSURLIsDirectoryKey error:nil];
 
    if ([isDirectory boolValue]) {
        NSString *name = nil;
        [fileURL getResourceValue:&name forKey:NSURLNameKey error:nil];
 
        if ([name isEqualToString:@"_extras"]) {
            [directoryEnumerator skipDescendants];
        } else {
            [mutableFileURLs addObject:fileURL];
        }
    }
}
 
NSLog(@"Files: %@", mutableFileURLs);

See Also

Discovering Directory Contents

contentsOfDirectoryAtURL:includingPropertiesForKeys:options:error:

Performs a shallow search of the specified directory and returns URLs for the contained items.

contentsOfDirectoryAtPath:error:

Performs a shallow search of the specified directory and returns the paths of any contained items.

enumeratorAtPath:

Returns a directory enumerator object that can be used to perform a deep enumeration of the directory at the specified path.

NSDirectoryEnumerator

An NSDirectoryEnumerator object enumerates the contents of a directory, returning the pathnames of all files and directories contained within that directory. These pathnames are relative to the directory.

mountedVolumeURLsIncludingResourceValuesForKeys:options:

Returns an array of URLs that identify the mounted volumes available on the device.

subpathsOfDirectoryAtPath:error:

Performs a deep enumeration of the specified directory and returns the paths of all of the contained subdirectories.

subpathsAtPath:

Returns an array of strings identifying the paths for all items in the specified directory.