Debugging Game for iOS Lab

In this lab, we'll be playing a game where each level requires using certain debugging skills to find and fix a bug. Once the bug is fixed, you'll be able to advance to the next level.

Note: The game saves your progress as you complete each level (using UserDefaults). If you want to go back to the beginning of the game, simply uninstall the app and you'll start from Level One.

Getting Started

The checkpoints below should be implemented as pairs. In pair programming, there are two roles: supervisor and driver.

The supervisor makes the decision on what step to do next. Their job is to describe the step using high level language ("Let's print out something when the user is scrolling"). They also have a browser open in case they need to do any research. The driver is typing and their role is to translate the high level task into code ("Set the scroll view delegate, implement the didScroll method").

After you finish each checkpoint, switch the supervisor and driver roles. The person on the right will be the first supervisor.

Level 0: Setup

1. Download the game.
2. Open Debugging.xcworkspace and run the app on an iPhone 6s Simulator (this is important as one of the levels requires an iPhone 6s).
3. Once running, you should see a screen that launches the game.

Level 1: The dreaded key-value coding compliant error

This is one of the most common exceptions you'll run into when first learning iOS.

1. Find LevelOneViewController.swift and LevelOneViewController.xib.
   • Xib's are an alternative to using a storyboard. They allow you to specify individual screens instead of laying out the entire app in the storyboard.
2. Fix the crash to move on to the next level.

Level 2: Terminating app due to uncaught exception?!?

It's really tricky to debug an issue when the exception bubbles up all the way to the AppDelegate and you have no idea where the original problem is. In this level, we'll use the Exception Breakpoint to capture the issue as soon as it happens.

1. Find LevelTwoViewController.swift and LevelTwoViewController.xib.
2. Set up an exception breakpoint.
3. Find and fix the crash to advance to the next level.

Level 3: The Button doesn't work

1. Find LevelThreeViewController.swift and LevelThreeViewController.xib.
2. There are a variety of reasons that a button might not work as you expect it to. The hint for this level is that it has something to do with the view hierarchy.
3. There's a really handy Debug View Hierarchy tool in Xcode that will help you troubleshoot.
4. Once you can figure out why the button isn't registering taps, fix it to advance to the next level.

Level 4: Dude, where's my tableView?

1. Find LevelFourViewController.swift and LevelFourViewController.xib.
2. There's supposed to be a tableView that shows a list of movie titles.
3. There are no hints on this level. You'll need to use a combination of setting breakpoints, stepping through code, and using the debug area to print and examine variables.
4. Once you are able to get the tableView cells to show up, tap on any of the cells to advance to the next level.

Level 5: Why are the descriptions wrong?

1. Find LevelFiveViewController.swift and LevelFiveViewController.xib.
2. If you scroll down and look closely at the movie descriptions, you'll notice that a lot of them are wrong.
3. Your objective on this level is to fix the bug so that each movie has the correct description or no description (if one wasn't provided).
4. Once you fix the bug, tap on any cell in the table to advance to the next level.

Level 6: AutoLayout

1. Find LevelSixViewController.swift and LevelSixViewController.xib.
2. This is a tricky level as it has to do with AutoLayout not being happy.
3. If you take a look at the output window, you'll see a warning Unable to simultaneously satisfy constraints. The objective for this level is to fix the AutoLayout constraints so that this warning goes away.
4. To fix this warning, you'll need to read up on Visual Format Language (VFL). VFL is a way to specify AutoLayout constraints using text.
5. Xcode uses VFL to tell you about the constraints that are conflicting so you'll need to understand this output and then fix the constraints in LevelSixViewController.xib.
6. Once the warning no longer appears, tap on Finish Level to complete the game!