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Defining Methods

4:00 with Jay McGavren

We've shown you how to call methods that Ruby defines for you. Now let's learn how to define your own methods.

  • Defining a method
    • def keyword
    • method name
    • method body: one or more lines of code that will be run when method is called
    • lines of method body are usually indented to make it clear they're a part of the method, although this isn't required
    • end keyword
def wait
  puts "Waiting..."
  sleep 3
  puts "Done"
end

def count_to_three
  puts 1
  puts 2
  puts 3
end
  • Valid method names
    • All lower case
    • Numbers are legal but rarely used
    • Separate words with underscores. This is called snake case because it makes the name look like it's crawling on the ground.
  • Call a method by typing its name in your code
count_to_three
wait
  • Can call a method as many times as we want
count_to_three
count_to_three

Here I've created another file named temp.rb that contains some new Ruby code. 0:00
Lines 1, 2, and 3 display a message that we're waiting, pause for 0:04
3 seconds, and then print another message that we're done waiting. 0:08
Lines 4, 5, and 6 count from 1 to 3. 0:13
These are two separate tasks in the same program, but it's hard to tell at a glance 0:17
which lines belong to which task, or what task they're supposed to be doing. 0:21
It's easy to define your own methods in Ruby. 0:26
You start with the def keyword, short for 0:28
define, followed by the name of the method you want. 0:31
So let's create a new method here named wait. 0:34
And next we're going to need a method body, that's one or 0:37
more lines of code that will be run when the method is called. 0:39
The lines of a method body are usually indented to make it clear that they're 0:43
part of the method, although this isn't required by the Ruby interpreter itself. 0:47
But it's a very common standard practice. 0:51
I would definitely recommend indenting your method lines. 0:53
So we're just going to take these first three lines of existing code and 0:56
put them inside a wait method. 1:00
The end of the method is marked by the end keyword. 1:02
And the end keyword should be aligned with the def keyword at the start of 1:07
the method. 1:10
So we'll convert those first three lines of code to a wait method. 1:11
And now let's define a count_to_three method to hold the remaining code. 1:15
We'll just take those existing lines of code and 1:25
indent them to form the body of the second method. 1:27
And again, we'll end the method with the end keyword. 1:31
You don't get to use just any character you want in a method name. 1:34
Generally speaking, method names should be all lowercase. 1:38
You can add numbers into them, but those are rarely used, so try to avoid that. 1:41
If there are multiple words in your method name, 1:45
you should separate them with underscore characters. 1:47
This style is called snake case, 1:51
because it makes the name look like it's crawling on the ground. 1:53
Now that we've defined the methods, we need to call them so 1:56
that they're actually executed. 1:58
We do that just like we did the predefined methods, 2:00
we simply type the name of the method to call it. 2:03
So count_to_three will call the count_to_three method that we've defined, 2:05
and wait will call the wait method that we've defined. 2:11
Let's hit Command + S to save that, Ctrl + S if you're on Windows. 2:16
And click down in the console area to try running it again. 2:21
Up arrow to bring up the previous command. 2:25
And you can see that our call to count_to_three causes the count_to_three 2:29
method to run and print the numbers 1, 2 and 3. 2:33
And then the call to wait causes the wait method to run and print the message, 2:36
waiting, then sleep for 3 seconds, and then print the message, done. 2:43
We can call a method during a program as many times as we want. 2:47
So let's add a couple additional calls to count_to_three down here. 2:50
I'll just copy the first call and paste it in a couple more times, save my work. 2:54
And re-run it from the console. 3:01
And you can see that it calls count_to_three once. 3:03
It calls wait once and then it calls count_to_three two more times down here. 3:07
Now that we understand method calls a little bit better, 3:13
let's go back to our widgets.rb file by clicking on it here on the side bar. 3:15
And let's implement our welcome message to the user. 3:21
We can do that with the single call to the puts method. 3:23
We'll pass it a string with the message, Welcome to the widget store!, 3:26
close the string with a pair of double quotes and save that. 3:33
And then click down here in the console to run it. 3:39
We do that with ruby widgets.rb. 3:42
And you can see that it prints our welcome to the widget store message. 3:48
Our program is displaying a welcome message to the user. 3:53
We can cross the first requirement off our list. 3:56

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