You can use NSFileWrapper as a package directory in document-based applications.
In your application Info.plist file, state that your document type is a package or bundle (key LSTypeIsPackage with value YES).
In your NSDocument subclass, implement the following methods for reading and writing. In this example, I’m assuming the corresponding model instance variables are pdfData and signatureBitmapData, which are stored in the package directory under MainDocument.pdf and SignatureBitmap.png, respectively.
- (BOOL)readFromFileWrapper:(NSFileWrapper *)dirWrapper ofType:(NSString *)typeName error:(NSError **)outError { NSFileWrapper *wrapper; NSData *data; wrapper = [[dirWrapper fileWrappers] objectForKey:@"MainDocument.pdf"]; data = [wrapper regularFileContents]; self.pdfData = data; wrapper = [[dirWrapper fileWrappers] objectForKey:@"SignatureBitmap.png"]; data = [wrapper regularFileContents]; self.signatureBitmapData = data; … return YES; } - (NSFileWrapper *)fileWrapperOfType:(NSString *)typeName error:(NSError **)outError { NSFileWrapper *dirWrapper = [[[NSFileWrapper alloc] initDirectoryWithFileWrappers:nil] autorelease]; [dirWrapper addRegularFileWithContents:self.pdfData preferredFilename:@"MainDocument.pdf"]; [dirWrapper addRegularFileWithContents:self.signatureBitmapData preferredFilename:@"SignatureBitmap.png"]; … return dirWrapper; }
From the user perspective, the package directory shows up in Finder as if it were a single file, much like Xcode .xcodeproj directories or application bundles.