Classes folder not appearing in Groups & Files Xcode

The code files have suddenly disappeared from the 开发者_如何学编程left tree pane on my Xcode. I tried to drag and drop the classes folder from the file system but this starts giving syntax errors. Please help.

---

If the project builds then you haven't deleted them, you've probably dragged them into another group[ by mistake :)

Open all the other groups and you might see the Classes folder as a subfolder. Just drag it back out again.

---

NB Go to Build->'Clean all Targets' and then build it again. If it builds without errors then my answer is probably right. If it doesn't build then I'm absolutely wrong :)