Variables

Quick reference

• 00:04 In this video I want to talk about variables.
• 00:06 And variables are just probably the most important thing in
• 00:10 any programming language.
• 00:11 And you're going to use these forever always every day.
• 00:15 So a variable is just, think of it like a bucket, and
• 00:18 you can put things into it and then take them out later on.
• 00:21 It's a box that you can contain things in.
• 00:23 It's a box you can put things in.
• 00:25 So to create a variable, you just name it, and
• 00:28 let's call this name not very good name, but that's our variable.
• 00:31 And to put something in our variable, we just do = and
• 00:34 I'm just going to type John Elder.
• 00:37 If we save this, now we have our variable, we've created it.
• 00:40 So if we save it and run this program now, nothing happens because we haven't
• 00:45 told our program to do anything with that variable.
• 00:47 We've just created it.
• 00:48 So whenever you create a name for a variable,
• 00:51 it's a good idea to use a description.
• 00:54 So name is not a very good one.
• 00:56 Let's say we were building a program for a shopping cart.
• 00:59 This might be customer_name, that's a better variable name.
• 01:04 So you want to be descriptive,
• 01:05 as descriptive as possible with your variable names.
• 01:07 Another thing is they have to be lowercase.
• 01:10 They have to start with lowercase.
• 01:12 You cannot start this with an uppercase letter.
• 01:15 You see it changes and
• 01:16 the reason why is because Ruby uses uppercase variables to name classes.
• 01:21 And we're going to talk about classes much later on in the course.
• 01:24 But for now just understand you can't have an uppercase variable name.
• 01:27 Also when you have two words customer and
• 01:30 name, the convention in Ruby is to use this underscore.
• 01:33 A lot of programming languages use something called camel case,
• 01:36 which is this.
• 01:38 It's like a hump, like a camel has a hump.
• 01:40 So underscore customer, upperscore name.
• 01:42 Now, you can do this, you're not going to get an error or anything.
• 01:45 But the convention in Ruby is to use underscores, everybody does it so
• 01:49 you should too, so here we go.
• 01:51 Now this variable has been created.
• 01:53 We didn't have to initialize it.
• 01:54 Now in a lot of programming language you have to
• 01:59 initialize customer_name before you can use it.
• 02:04 Not so with Ruby, all you have to do is name it, slap something in and
• 02:08 it's ready to go, which is a great, great thing about Ruby.
• 02:11 So to use this, we can just we can do whatever we want.
• 02:14 And as you see, as I start to type it, our program already knows it exists.
• 02:18 So I can hit tab and it'll just pop it right in.
• 02:21 So if we save this, come here and run it, we see John Elder so very, very cool.
• 02:26 You can see here I've put a string in customer_name John Elder,
• 02:31 you could just as easily create something called price = 1999.
• 02:37 Now if we puts price, we get 1999.
• 02:42 So notice this is a number, this is a float, we put a float in a variable.
• 02:46 We didn't have to tell our program, hey,
• 02:48 we're going to use numbers in this variables.
• 02:50 A lot of programming languages you have to declare your variables to be number
• 02:55 associated, not so with Ruby.
• 02:56 You just slap your thing in there and go.
• 02:58 Likewise we can change things, we can go customer_name
• 03:04 = Bill puts customer_name, run it.
• 03:11 The first time we output it, it was John Elder.
• 03:14 We changed it down further in the program output it again and it changed to Bill.
• 03:19 So these are fluid, you can put things in, you can take them out,
• 03:23 you can replace them, we could of changed this to 21, save it, run it again.
• 03:29 The first time it's John Elder, the second time it's 21.
• 03:32 So you can change the data type of a variable.
• 03:35 Up here the data type was string because we put a string in there.
• 03:39 Down here the data type was integer because we put a number in there,
• 03:42 so very flexible with what you can do with variables with Ruby, which is very cool.
• 03:47 And like I said, you're just going to use these forever,
• 03:49 variables are just a cornerstone of all programming.
• 03:51 They're going to be in every program you ever write, yeah.
• 03:54 In the next video, we're going to talk about assignment operators.

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