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What is a getter and how do we use it?

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Class Getters.docx
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Quick reference

Class Getters

Getters let you get things from your class.

When to use

Use them whenever you create any class.

Instructions

To create a getter:

class Square
    def initialize(side_length)
        @side_length = side_length
    end
    
    # Create Getter
    def side_length
        return @side_length
    end
end

Hints & tips

  • Getters let you get stuff from your class
  • Getters should be named the same as their instance variable
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  • 00:04 In this video I want to talk about getters.
  • 00:06 So with classes you have something called a getter and a setter, and
  • 00:10 it's just getter, G-E-T-T-E-R-S.
  • 00:12 And a getter allows you to get something from your class, right?
  • 00:17 So far we've initialized, that we've passed in our side length, but
  • 00:20 we can't really do anything with it.
  • 00:22 We need to set a getter, create a getter method in order to be able to use that
  • 00:27 side length outside of our program, right?
  • 00:29 So to do that, we just create another method, and you generally want
  • 00:34 to name your getter the same name as whatever the variable thing is,
  • 00:39 the parameter that you passed into it.
  • 00:42 So we're going to go side_length, okay?
  • 00:47 And generally what you're going to want to do with a getter is just return
  • 00:52 your instance variable of side_length or
  • 00:55 whatever parameter you're looking to turn into a getter.
  • 01:00 So if we save this now, so here's where we initialize our square and
  • 01:04 we've passed in 20.
  • 01:06 Now, to use that 20 for something in the future,
  • 01:11 we can call puts my_square.side_length.
  • 01:15 As I start to type it already realizes, this method exists and we can call it.
  • 01:19 Now, the side_length is now a method of the square class, right?
  • 01:23 So if we save this and hit Reload, boom we get 20.
  • 01:27 Likewise if we change this to 10, we get 10.
  • 01:31 So you can see this adding a dot and putting method on the end, the very object
  • 01:36 orientee type of thing and getters are very, very fundamental to classes.
  • 01:41 And in the next video we're going to talk about setters.
  • 01:43 You can guess what they do but not too difficult of a concept to wrap your brain
  • 01:48 around this getter. And we can start to play around
  • 01:53 with these things and sort of add functionality to our class.
  • 01:56 What else can you do with a square?
  • 01:58 Let's call the area.
  • 01:59 So define area.
  • 02:03 And how do you find the area of a square?
  • 02:04 It's side length times side length, right?
  • 02:07 So we can go return @side_length
  • 02:13 times @side_length and that works.
  • 02:20 So now we can save this and come down here and type in area.
  • 02:26 We save it, boom, our area is 100 because 10 times 10 is 100.
  • 02:31 If we change our side length to 20, 400,
  • 02:34 sort of off topic from a getter, but I just flesh this out a little bit more.
  • 02:39 You can do parameter, you can do whatever different things you want your square
  • 02:43 class to be able to do, and it's just really cool.
  • 02:46 So that's getters, you generally want to create a getter for
  • 02:49 all of your parameters that you pass in.
  • 02:52 In the next video, we're going to look at setters.

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