Methods in Karel

In the last chapter, we briefly introduced using a method to turn Karel right. But what is a method? And why would we want to use them?

The Basics

A method is a way to teach Karel a new word, or a new command. Methods allow us to break our program down into smaller parts and make it easier to understand. A program with many smaller methods is easier to read and fix than a program with one very large method.

The format of a method looks like:

private void myMethod()
{
    /* code goes here */
}

Naming is crucial

Here is another example:

private void buildPyramid()
{
    /* code goes here */
}

From the name of our method, buildPyramid(), it is very clear what the method does. There are a few rules for how you name your methods:

• Method name should start with a letter, and cannot have any spaces.

• Every new word in the name starts with an uppercase letter.

• The name should describe what this function does.

• The name should start with an action verb, and sound like a command.

Defining a method vs. calling a method

When we want to create and use new methods, there are two parts: Defining a method and calling our method after we have defined it.

Defining a method: Teaching Karel the new command. In other words, writing out the instructions for this new action.

Calling a method for Karel: Actually getting Karel to do the command. Actually causing the action to happen.

For Karel to know how to do the command, we will first need to teach Karel the command.

Example

Defining turnRight(): Karel, when you want to turn right, the instructions are to turn left three times.

Calling turnRight(): Karel, turn right.

Example: Defining turnAround()

Let's teach Karel how to turn around. Here is our class in a code editor:

public class TurnAroundKarel extends Karel{

    public void run()
    {
        move();
    }

}

If we try and call turnAround() before we define the method, there will be an error: Uncaught ReferenceError: turnAround is not defined.

public class TurnAroundKarel extends Karel{

    public void run()
    {
        move();
        turnAround(); // Won't work
    }

}

Instead, we need to define turnAround() in another method.

public class TurnAroundKarel extends Karel{

    public void run()
    {
        move();
    }

    //defining our method
    private void turnAround()
    {
        turnLeft();
        turnLeft();
    }

}

Now that we have defined our method, we can call it in the run() method.

public class TurnAroundKarel extends Karel{

    public void run()
    {
        move();
        turnAround(); //calling our method after it has been defined
    }

    private void turnAround()
    {
        turnLeft();
        turnLeft();
    }

}

And that's it! You should now be able to define and call methods properly to make your code cleaner and easier to understand.