Classes Part 2

Quick reference

• 00:04 In this video, we're going to continue on with classes.
• 00:07 In the last video we created a class, and we created an initialize method.
• 00:11 And now, how do we do something with this?
• 00:14 How do we use this?
• 00:15 Well, to start out you need to create an object to initialize this thing.
• 00:20 So let's create it, let's call it my_square.
• 00:24 Call it whatever you want, doesn't really matter.
• 00:26 And =.
• 00:27 Now, to kind of fire this thing up and make it work,
• 00:30 we type in the name of the class, Square, and then .new.
• 00:34 That's sort of how you initialize it.
• 00:36 Now, you would maybe think you would type in .initialize, but no, for
• 00:40 some reason it's .new
• 00:42 And then, be sure to pass your parameter.
• 00:44 So let's say we want a side_length of 5.
• 00:47 So now if we save this, come up here, and run our program, nothing happens,
• 00:52 because all we've really done here is kind of start our class.
• 00:55 We fired it up, but it doesn't really do anything yet.
• 00:57 In fact, we can come up here and we can go puts my_square,
• 01:02 because now our square is this guy right here,
• 01:05 this my_square is an object of the Square class.
• 01:09 It is a square, and we can puts it to the screen.
• 01:12 But if we do, you're going to see it's kind of weird here.
• 01:15 We get this gobbledygook.
• 01:17 All this is, this is an address in memory where our square resides.
• 01:23 Doesn't mean anything to us at all.
• 01:24 We can go a little bit further and type in inspect,
• 01:28 which will let us inspect our square.
• 01:31 And you see, now it says the same weird gobbledygook, but
• 01:35 it also has our instance variable, our side_length=5, because we passed in 5.
• 01:41 If we changed this to 10 and ran it, now it's going to say side_length=10.
• 01:47 Every time we sort of initialize our class and
• 01:51 pass it stuff, a new instance of our Square class runs.
• 01:55 And you'll notice, so this is an address in memory where our square resides.
• 02:00 Every time we run this, you'll see we get a new address because it's creating
• 02:04 a whole new square every time we run it.
• 02:05 So a lot of these things I'm talking about are going to be a little abstract and
• 02:10 weird, you might not understand exactly what's going on, and
• 02:13 we're just going to motor through this and start using these things.
• 02:16 And as we do, you'll start to see, okay, this starts to make more sense.
• 02:20 Right now I just want to show you the format of a class, how you start them.
• 02:25 You initialize every class you ever create,
• 02:27 you're going to initialize like this, and pass in some sort of parameter, and
• 02:31 then set that parameter equal to an instance variable.
• 02:34 And we haven't really talked about instance variables,
• 02:36 I'll talk about them more in the next video.
• 02:39 But you know I mentioned earlier the idea of a t-shirt factory, and
• 02:42 a class is a blueprint?
• 02:44 I can come to it and I can say, I want a blue t-shirt, I want a black t-shirt.
• 02:48 Well, same thing here.
• 02:50 We've got a class with a square and we're saying,
• 02:52 I want a square with sides of 10, or, I want a square with sides of 20.
• 02:57 All of this stuff stays the same, but we can pass in our whatever we want into it,
• 03:03 to make our demands to get what we want.
• 03:05 So that's sort of an abstract concept, and
• 03:07 it'll become more clear, I promise, as we go on.
• 03:09 I know this is kind of weird at the beginning, but classes, super important.
• 03:13 In the next video we're going to talk more about instance variables.
• 03:16 So that's all for this video.

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