Create a folder inside documents folder in iOS apps

Question

I do that the following way:

NSError *error;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"/MyFolder"];

if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
    [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error]; //Create folder

I don't have enough reputation to comment on Manni's answer, but [paths objectAtIndex:0] is the standard way of getting the application's Documents Directory

http://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/StandardBehaviors/StandardBehaviors.html#//apple_ref/doc/uid/TP40007072-CH4-SW6

Because the NSSearchPathForDirectoriesInDomains function was designed originally for Mac OS X, where there could be more than one of each of these directories, it returns an array of paths rather than a single path. In iOS, the resulting array should contain the single path to the directory. Listing 3-1 shows a typical use of this function.

Listing 3-1 Getting the path to the application’s Documents directory

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

Swift 3 Solution:

private func createImagesFolder() {
        // path to documents directory
        let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first
        if let documentDirectoryPath = documentDirectoryPath {
            // create the custom folder path
            let imagesDirectoryPath = documentDirectoryPath.appending("/images")
            let fileManager = FileManager.default
            if !fileManager.fileExists(atPath: imagesDirectoryPath) {
                do {
                    try fileManager.createDirectory(atPath: imagesDirectoryPath,
                                                    withIntermediateDirectories: false,
                                                    attributes: nil)
                } catch {
                    print("Error creating images folder in documents dir: \(error)")
                }
            }
        }
    }

I don't like "[paths objectAtIndex:0]" because if Apple adds a new folder starting with "A", "B" oder "C", the "Documents"-folder isn't the first folder in the directory.

Better:

NSString *dataPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/MyFolder"];
if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
    [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error]; //Create folder