Learn to Program

The methods new and initialize work hand in hand. You use new to create a new object, and initialize is then called automatically (if you defined it in your class). They pretty much happen at the same time. How do you keep them straight?

You can think of these as being “under the hood”: unless you’re an automobile mechanic, all you need to know is the gas pedal, the brake pedal, and the steering wheel. These are the public interface of your car. How your airbag knows when to deploy, on the other hand, is internal to the car; the typical user (driver) doesn’t need to know how that w

Here, you create a proc—which I think is supposed to be short for procedure, but far more important, it rhymes with block—that holds the block of code. You then call the proc three times. This process is a lot like a method. In fact, blocks (and thus procs) can take parameters exactly like methods do. Here’s how it looks: ​1: do_you_like = Proc.​ne

One of the cool things you can do with procs is create them in methods and return them.

Blocks and procs are definitely some of the coolest features of Ruby. Some other languages have this feature, though they may call it something else (like closures or lambdas), but many don’t, and it’s a shame. They are a joy to use.

That’s what the initialize method is for; as soon as an object is created, initialize is automatically called on it (if you have defined it). It looks like any other method, except that it’s called initialize.

Now that you have your public interface, it’s time to define your private methods: methods that cannot be called externally, but that your public methods can call. One of these is passage_of_time, and you also want a few others. To make these methods private, you precede them with the keyword private.

Let’s start with a short example: ​1: toast = Proc.​new​ ​do​ ​2: puts ​"Cheers!"​ ​3: ​end​ ​4: ​5: toast.​call​ ​6: toast.​call​ ​7: toast.​call​ ​<= Cheers! ​ Cheers! ​ Cheers!

Internal to a car object, though, much more would need to be going on; other things a car would need are a velocity, an orientation, and a position. These attributes would be modified by pressing on the gas or brake pedals and turning the wheel, of course, but the user wouldn’t be able to set the position directly (which would be like warping). You