Once Upon a Puzzle

Once while I was online looking for a job, a company’s job application form requires one to solve a puzzle before one can submit, the question states:

Only the white block is movable, in the left, right, up, and down direction. Give the shortest sequence of steps to go from A to B.

So I made an app for me to try out this puzzle.

Now fast forward, three years later, I still don’t know the answer, but yesterday I came across this project while I was cleaning up my repositories. I cloned it and decided to have a look, why not? Within half an hour, I finished refactoring and some UI refinements, as this is 1.1, not 2.0. Surprisingly I learned a lot during this cleanup:

• Upgrading from Swift 2 to 5 for such a small code base only needs less than a minute.
• Refactoring reduces a lot of code; cloc shows code lines went from 346 down to 157. The program becomes more straightforward, as comment line count went down too.
• Without any 3rd party framework dependencies, from iOS to Catalyst is just two checkboxes away.
• Avoid assigning cgColor to layer properties; they don’t support dark mode at all.
• If you go with Storyboard, Embed in View is your friend; it makes Auto Layout dead simple.
• Even in Storyboard, watch out for violating the DRY principle. When there are many copies of @IBDesignable views, and most of them have the same style, move the appearance setup into source code.
• Global constant (let alone variable!) is problematic. You can do better.
• Every crash on force-unwrapped nil is an opportunity to change the function’s return type to Optional and apply guard against its assignment.

I created this project on October 10, 2016, while I was looking for a job. Three days later, I got my first job; thus, this toy project always has a special meaning to me.