What design pattern is this?

Question

I'm struggling to come up with the name of a design pattern that I need to write about. I've been lead to think it was abstraction but apparently not.

Let's say I had a driver class which has a Drive method:

public void Drive()
{
    if(IsOnGasPedal)
    {
        //Lots of code
    }
    if(IsOnBrake)
    {
        //Lots of code
    }
    if(IsOnClutch)
    {
        //Lots of code
    }
}

And I change the method to:

public void Drive()
{
    if(IsOnGasPedal)
    {
        Car.Gas()
    }
    if(IsOnBrake)
    {
        Car.Brake()
    }
    if(IsOnClutch)
    {
        Car.Clutch()
    }
}

I have moved the complex and long code into separate methods in my Car property so that the Drive method is more organised. This is an example of refactoring but that is not the word. I thought it was either encapsulation or abstraction but I can't get any solid answers. What is this pattern called?

I don't think this is a "design pattern" per se. Encapsulation and/or abstraction (which are not patterns but goals or ideals) probably are the most precise single words for it. — Ixrec, Jun 28 '15 at 18:54
see also [Is it OK to split long functions and methods into smaller ones even though they won't be called by anything else?](http://programmers.stackexchange.com/q/195989/31260) and multiple questions [linked](http://programmers.stackexchange.com/questions/linked/195989?lq=1) to it — gnat, Jun 28 '15 at 18:57
Have you already driven on a Ralley? On almost every curve you need to operate all 3 pedals with your 2 feet. Your code doesn't look like as it could handle that properly. — ott--, Jun 28 '15 at 21:13
@ott-- You do realise this is just an example? This was written purely to show the pattern in question. — Frayt, Jun 29 '15 at 00:42

Ben Aaronson · Answer 1 · 2015-06-28T20:10:18.387

To be clear, none of "refactoring", "abstraction" or "encapsulation" are design patterns.

Neither is what you posted. As you say, it is a refactoring. Specifically, it is the one that Martin Fowler named Extract Method. The definition is "Turn the fragment into a method whose name explains the purpose of the method.", which is precisely what you are doing.

It does also fall under the definition of abstraction. Structure and Interpretation of Computer Programs, for example, describes this as:

[The means] by which compound elements can be named and manipulated as units.

Compound elements, in this case, would refer to the multiple expressions which make up the extracted methods.

score 1 · Answer 2 · answered Jun 28 '15 at 20:02

1

Arguably it is simply the application of structured programming which was named long before design patterns were born.

As a refactoring, you can call what you have done 'Extract method'

answered Jun 28 '15 at 20:02

Pete Kirkham

1,798
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score 1 · Answer 3 · answered Jun 28 '15 at 22:52

Well I think people are missing the point that you're delegating the behavior that was once in the Driver class into the Car class, so it's not really Extract Method because otherwise it would be in the same class. This is either simple composition (not a DP) but if you want to be kind, it might be an implementation of Strategy, which some people do consider a design pattern.

What design pattern is this?

3 Answers3