Welcome back to our series on Xcode 9. Today we'll talk about automated tabs. To cover that in a live way, we'll also cover debugging and testing.

So here's some code that I've written, and I'd like to step through it one line at a time.

Breakpoint

So I hit the play button, and Xcode will build the app, start running it in the iPhone Simulator.

And when it hits the break point, it will automatically open the stack navigator, and show me where the current place is in the code.

stack navigator

It will show me the values that I've got, and as I step over each one...

variables view

Ok, now width is filled in.

I'll step over another one, now height is filled in.

And if I want to get a more detailed description of something, I can go over to the console, and type "po", which used to stand for "print object" in Obj-C. When they introduced Swift, they said, "well, people are just used to typing 'po' to get what they want, so... we'll just use that."

So...