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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
-
defkeyword - 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
-
endkeyword
-
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
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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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