- (NSFileWrapper *)fileWrapperOfType:(NSString *)typeName

                               error:(NSError *__autoreleasing *)outError {

    // Save data here ...

}

- (BOOL)readFromFileWrapper:(NSFileWrapper *)fileWrapper

                     ofType:(NSString *)typeName

                      error:(NSError *__autoreleasing *)outError {

    // Load data here ...

}

Problems

There’s a few gotchas with the .plist file. In order to create a NSDocument using Folder Bundles you’ll need to set the UTI Identifier for the Document  Type and the Exported/Imported UTIs. You’ll find this setting on the Info page for your Xcode Target.

1. My App doesn’t load saved bundles (NSFileWrapper), instead it just looks inside the folder.
2. I tried to undo the Export UTI by deleting it and remove the Identifier, but that doesn’t help.
3. By deleting the Identifier I can’t load “New documents”.

Solutions

There are two solutions, the second one is more robust, but the first will get you back to when it was working.

Solution 1: Revert back to Xcode template defaults

1. Remove all Exported UTIs
2. Open your App .plist file and remove the LSItemContentTypes from your App .plist file. You can’t see it in the Target -> Info page.
   1. NOTE: if you don’t delete an empty LSItemContentTypes array, then you won’t be able to open New files.
   2. If LSITemContentTypes is defined, it’ll ignore the “Bundle” checkbox (LSTypeIsPackage) See the Apple docs.
3. Make sure “Bundle” is checked on the Document Types on your Target’s Info page, or (LSTypeIsPackage on .plist file)
   1. This option is magic and auto generates a Identifier for you. (check your save file with “mdls” on the Terminal)
4. Don’t use an Identifier if you check the Bundle option (Document is distributed as a bundle)
5. Clean the Xcode project

Solution 2: Use the package UTI

You’ll need to add the correct LSItemContentTypes found in Apple’s documentation. I took a look at the Xcode project file with the Terminal utility “mdls” (See sample output below)

1. Set a unique identifier (Reverse DNS name) com.Your_Company_Name.Project_Name
   1. It needs to match theDocument Type and Exported UTIs
2. For a bundle, you’ll need to set the “Conforms To” for the Exported UTIs to “com.apple.package”
   1. Apple Docs: “A package (that is, a directory presented to the user as a file)”
3. I noticed Xcode project files also include, public.composite-content
   1. Apple Docs:  ”Base type for mixed content. For example, a PDF file contains both text and special formatting data”
4. NOTE: If you mistype com.apple.package, or leave it out, your file folder will be treated like a public.folder, and you’ll get folder behavior.
5. Clean the Xcode project

Working Icon and Bundle File

If all goes well you’ll now see the Icon (icns) file that you created in the Open dialog and the folder will appear to be a bundle.

Using MDLS to inspect your files

The only way it works as a bundle is if the “com.apple.package” ContentType is listed, otherwise something is wrong. Check your save files with the “mdls” command.

mdls MathAndArt.xcodeproj/

The idea was to make the boiler plate code disappear and make it easier for novice programmers to get an animated graphics window in as few lines as possible. Only four lines of code are needed to get the window running at 60 frames per second. You can subclass the framework and implement your own OpenGL animation or game project.

Edit (8/22/10): You don’t need to use pointers, I’ve updated the code example with working code.

// main.cpp
#include "GlutFramework.h"
using namespace glutFramework;
int main(int argc, char *argv[]) {
	GlutFramework framework;
	framework.startFramework(argc, argv);
        return 0;
}

The code uses a cross-platform (Windows/Mac tested) timer to create a constant frame-rate, which is necessary for animation projects. It’s under the MIT License, so feel free to use it as you see fit.

http://github.com/PaulSolt/GLUT-Object-Oriented-Framework

An Xcode 3.1 and Visual Studio 2010 project is hosted on github to support Mac and Windows. There is no setup on the Mac, but Windows users will need to configure GLUT. I plan on posted tutorials on how to get setup on both platforms. For now, look at the resources section below.

Animated teapot

Resources:

• Previous Post: http://paulsolt.com/2009/07/openglglut-classes-oop-and-problems/
• GLUT for Windows: http://www.xmission.com/~nate/glut.html
• Visual Studio and GLUT setup: http://www.cs.uiowa.edu/~cwyman/classes/common/howto/winGLUT.html
• Old Post on GLUT in Eclipse: http://www.paulsolt.com/GLUT/