Running from Xcode 6.1 - Linker errors

I had the same problem; I have cleaned my project (cmd+shift+k) and this fixed the bug.

Cleaning and re-building the project did not help me. In my case, I had a class which was a simple UIViewController, implementing a datasource and delegate at the same time:

   public class MyViewController: UIViewController, UIPickerViewDelegate,                    UIPickerViewDataSource {      ...

When I removed the two protocols (UIPickerViewDelegate and UIPickerViewDataSource) and removed all methods from the class which implemented them, then I could build without an issue. I then re-added the methods only, it built, then went back to what I had before and - get this - it built. Ugh.

So there seems to be some issues with the Swift linker. Play around with the class in question, simplifying it until it builds, then add piece by piece back.

What Im doing is to create sks files using XCODE 6.1, and for the rest of the work then I use XCODE 6.0.1.

If you want to change something on your sks you have to change again to 6.1. Never select a sks file running under 6.0.1