In the Guidebook app Chris has a section on Debugging Xcode problems. One of the ways he shows is to use breakpoints and then the po command to look at. a variable. This works fine but here is another method:
For the variable you want to see enter: "let _ = print(variableName) " inside of your code (remembering the scope of the variable). This will print the variable when you run the code from Xcode. No breakpoint needed.