If you get stuck or just want to check your code against the answer, you can download the completed app that contains all the solutions to the challenges up to this point. All the steps in the challenges are marked out in the code as comments to help you easily navigate. Simply head over to the top left corner on this screen "Course Resources" Button.
Note: there are many ways of achieving the same outcome with code, just because you did it a slightly different way doesn't mean it's wrong. As long as you achieve the desired outcome then you've succeeded. After all, learning to code is just learning how to make the computer obey your commands!