Writing a new method

As programmers we like to split up our tasks, and do one thing after another. This allows us to focus on one small task, and once we’ve solved it, we move on to the next one.

When you need to add some new functionality to your program you’ll often find yourself thinking “I should add a method for this”: methods add behaviour.

Now, the first thing you should ask yourself is: “What is it that this method should do?” The answer to this gives you a hint for a good method name.

Let’s say you are working on an application that deals with emails, and the thing you are trying to accomplish is formatting an email. So your method name can be format_email.

With this first task solved, knowing the method name, you can already go ahead and write down the method definition:

def format_email

While this is a pretty useless method, since it does nothing at all, it already is a valid method. So that’s good progress already: you’ve made the first step.

The next question to ask is: “Does this method need to be given any information in order to do its thing?” The answer to this question specifies the method’s arguments list.

In our example, the answer probably is that, in order to format an email, it needs the email.

So you can now add the argument list to the method:

def format_email(email)

With these two things solved you can now start thinking about implementing the method body. How can you transform the email into some formatted text?

You’d add a new line between def and end, and make sure it’s indented by two spaces (hit tab, unless your editor does it for you), and start focussing on the code that makes up the method body:

def format_email(email)

You see how we’ve split up the task of writing a new method into three smaller tasks, and worked on each one of them after another.

Even though this might seem trivial at first, we recommend you get into this habit, too.

Btw, good editors help you format things. For example, when you are on a line that starts with def something, and at the end of the line hit return, Sublime will already indent the next line for you by 2 spaces. If you now type end, then Sublime will notice that you are closing the method, and outdent it again, so def and end sit on the same level. Smart, isn’t it?

Also, you’ll notice that when you type an opening parenthesis (, then Sublime will add a closing one ) too, but keep your cursor placed between them, so you can type the argument list where it belongs.

Exercises: Now would be a good time to do some of the exercises on methods.