We've seen quite a few patterns so far, and I'm glad so many people like them.

They turned out to be the most popular posts I've ever written when it comes to development. Thanks! :)

A little overview for the late joiners:

Today we'll have a look at the Adapter Pattern.

As usual, the definition: "Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces."

To continue on our little game, we received a third party library from another team, containing some buildings to include in our game.

The developers of this library didn't work with IBuildings however, but call it a Structure, making all of our code which interacts with IBuilding unusable.

If we look at the definition, we can see the Adapter Pattern is the perfect solution for this, since we need to convert the interface of the third party Structure into the IBuilding we expect, so that they can work together as if their interface was compatible.

Let's have a look on how their interface looks like first.

Third Party Library - Adaptee

There are some differences in the logic used in their implementation. We both have a Description, but the way we manage Power consumption is totally different.

Time to adapt their interface to the one we expect.

We'll do this by creating a new class, a so called adapter, which implements the IBuilding interface, since we expect that one, and which uses composition to encapsulate a Structure.

Adapter Class

As you can see, our Adapter is actually behaving as an IBuilding to the rest of our code, adapting the calls to our interface into the third party their interface.

And that's it really! The easiest way I remember this pattern is by thinking of electrical adapters, changing the socket from US to UK, or transforming the voltages.

Time to have a look at the full diagram, with the official names written against it again:

Adapter Pattern Class Diagram

Let's also write some test code to see the Adapter Pattern in action.

Testing Adapter Pattern

We can re-use all of our existing code with the new Structures, since it's behaving like an IBuilding right now.

I've uploaded the solution again to have a look at.

Feel free to leave any feedback.

Some additional information on the Adapter Pattern:

Reacties: 3
  • Broke the record of unique visitors yesterday, all during my Wordpress upgrade ;) Thanks to all of you, new record is standing at 1400 readers in a day :p

  • Johan

    I'd just wanted to say that this series of articles about patterns is really good. Please keep up the good work!

  • Just as usual David, nice article!

    That one is among the easiest pattern there is in the book. Of course, when merged with the other patterns yield great result.


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