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Design Patterns The Adapter Pattern
Human Computer Interaction (HCI 308)
Kenyatta University
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Design Patterns: The
Adapter Pattern
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- Reply •
ehelguero • 4 years ago Really nice article! I ́m going to try it. 29 △ ▽
- Reply •
Marcos Borunda • 4 years ago What I find amazing about Design Patterns is how stuff that you might already figure out by yourself, while coding, actually is a thing and has a name. Knowing the name for a design pattern and a structured definition make things clear and easy to express with your team. 20 △ ▽
- Reply •
techniczny > Marcos Borunda • 4 years ago What you really should find, is that if you knew about design patterns before when learning programming, you wouldn't need to figure it out later by yourself. 3 △ ▽
- Reply •
Mark Fox • 4 years ago Nice example. Now, I will be a pedantic moron: class-names that aren't CamelCase look sloppy and weird. 6 △ ▽
- Reply •
Nathan Daly • 4 years ago Great article :) 3 △ ▽
- Reply •
Xin Zheng • 4 years ago Nice article! Thanks!!! 3 △ ▽
- Reply •
Mikle Kozachoc • 3 years ago What about, if we alredy have used sendPayment() and in same time PayPal chenged name of method? 2 △ ▽
- Reply •
Levent Atan > Mikle Kozachoc • 10 months ago I think that would be a perfect case where adapter pattern can be applied. I mean I should be using a payment solution already and find out another (new) one (instead of a replacement) which doesn't comply with the existing interface. △ ▽
- Reply •
Avinash > Mikle Kozachoc • 3 years ago In that case we need to replace new method name in pay method of our adapter class only.
public function pay($amount) { // Old Line $this->paypal->sendPayment($amount); // New line with new method name $this->paypal->sendPayment2($amount); }
Hope this is clear △ ▽
- Reply •
UseMeAbuseMe4Ever > Avinash • 6 months ago I think technically, you would need to change it in two places right? In the Adapter pay method AND in the concrete class. △ ▽
- Reply •
Mikle Kozachoc > Avinash • 3 years ago ok, but if we did not implement adapter before. △ ▽
- Reply •
Avinash > Mikle Kozachoc • 3 years ago In that case you will need to change at all places where you have used that method. I have explained the same in problem section of this article. Hope that's clear. △ ▽
- Reply •
Michael Lawson • 4 years ago Hooray for underutilized design patterns! 2 △ ▽
- Reply •
Hari krishna • 4 years ago What is the use of social adapter interface? What happens when we implement a class without interface? 1 △ ▽
- Reply •
Wesam Alalem > Hari krishna • 3 years ago Program to interface, not implementation, check the first answer for SO question regarding this topic: stackoverflow/qu... △ ▽
- Reply •
Bruce Lampson • 4 years ago Good job Avinash Zala! Very comprehensible. I wrote a simple presentation few weeks ago explaining this pattern. In my example i use a global adapter that should be compatible with many mail clients via dependency injection. I would like to share this example with all of you. smsnica/reve... (Simply press your down arrow to checkout the implementation) 1 △ ▽
- Reply •
Avinash > Bruce Lampson • 4 years ago Thanks for sharing... :) 1 △ ▽
- Reply •
D3F > Bruce Lampson • 3 years ago Hi Bruce,
Nice presentation, however you are missing a semicolon in smsnica/reve... at line 2 ;)
En you say $clint i think this must be $client, but you are using it consistent so nothing breaks.
But nice presentation, very straightforward. △ ▽
- Reply •
Bruce Lampson > D3F • 3 years ago Hey there D3F, Thanks for pointing that out! △ ▽
- Reply •
Julius Koronci > Bruce Lampson • 4 years ago Nice presentation and very self explanatory :) △ ▽
- Reply •
Nadeen Nilanka • 4 years ago Understood, great article! 1 △ ▽
- Reply •
Paweł P. • 4 years ago Patterns – like always in "price". 1 △ ▽
- Reply •
Shahzaib Khan • 4 months ago Error in code :- While changing "$this->paypal->sendPayment($amount);" to "$this->paypal->payAmount($amount);"
We also need to change "public function sendPayment($amount) {" to "public function payAmount($amount) {"
also in main "PayPal" class. △ ▽
- Reply •
Fun Zone • 8 months ago very helpful article. △ ▽
- Reply •
James Watadza • 2 years ago Good tutorial again. Ignore the morons who have never written a single tutorial but spend hours criticizing and shooting down the work of those who cared enough to take the time to teach others. △ ▽
- Reply •
Mukesh Singh • 3 years ago tutorial is amazing. please add more pattern △ ▽
- Reply •
Vhin Manansala • 3 years ago Great article, but I have a question.
What's the difference of using interface when using
class paypalAdapter{ private $paypal; public function __construct(PayPal $paypal) { $this->paypal = $paypal; }
public function pay($amount) { $this->paypal->payAmount($amount); } }
Seems to work fine?? △ ▽
- Reply •
Mohamed Wael • 3 years ago Very good article, thank you. △ ▽
- Reply •
Avinash > Mohamed Wael • 3 years ago Glad you liked this. △ ▽
- Reply •
manhee • 3 years ago It'd be better to rename "interface paymentAdapter" to " interface paymentInterface". △ ▽
- Reply •
gundholmu • 3 years ago Nice article and easy to understand. But I have some question about this pattern.
Why we need to create an interface class (paymentAdapter)? why we not just directly create an instantiate of PayPal class within the construct class of paypalAdapter? △ ▽
- Reply •
Ankush Thakur > gundholmu • 3 years ago Because by making all classes implement an interface, we can be sure all of them use the same function name for payment. If you were directly wrapping classes, you might mistakenly name one of the adapter functions as pay() and the other as payNow(), causing confusion to yourself. △ ▽
- Reply •
Yanwar • 3 years ago what adapter can be combined with the facade? △ ▽
- Reply •
Elfan Nofiari • 4 years ago One umbrella term for this would be single source of authority, or DRY, Don't Repeat Yourself. △ ▽
- Reply •
amorbytes • 4 years ago Very good explanation design patterns and how we can use it for solve our daily problem. △ ▽
- Reply •
tormahiri • 4 years ago thanks article and simple △ ▽
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Proceed
by Avinash Zala 8 Nov 2014 Difficulty:Intermediate Length:Short Languages: English
Design Patterns PHP OOP Programming Fundamentals
The Adapter Pattern Web Development
This post is part of a series called Design Patterns in PHP.
Design Patterns: The Facade Pattern
Design Patterns: The Decorator Pattern
In the last article, we looked at how the facade design pattern can be
employed to simplify the employment of any large and complex system using
only a simple facade class.
In this article, we will continue our discussion on design patterns by taking a
look at the adapter design pattern. This particular pattern can be used when
your code is dependent on some external API, or any other class that is prone
to change frequently. This pattern falls under the category of "structural
patterns" because it teaches us how our code and our classes should be
structured in order to manage and/or extend them easily.
Again, I'd like to reiterate that design patterns have nothing new over
traditional classes. Instead, they show us a better way to structure our
classes, handle their behavior, and manage their creation.
The Problem
In the above code, you can see that we are utilizing a PayPal class to simply
pay the amount. Here, we are directly creating the object of the PayPal class
and paying via PayPal. You have this code scattered in multiple places. So we
can see that the code is using the $paypal->sendPayment('amount
here'); method to pay.
Some time ago, PayPal changed the API method name from sendPayment to
payAmount. This should clearly indicate a problem for those of us who have
been using the sendPayment method. Specifically, we need to change
all sendPayment method calls to payAmount. Imagine the amount of code we
need to change and the time we need to spend on testing each of the features
once again.
The Solution
One solution to this problem is to use the adapter design pattern.
According to Wikipedia:
In software engineering, the adapter pattern is a
software design pattern that allows the interface of
an existing class to be used from another interface.
It is often used to make existing classes work with
others without modifying their source code.
In this case, we should create one wrapper interface which makes this
possible. We will not make any changes in the external class library because
we do not have control over it and it may change any time.
Let's dig into the code now, which shows the adapter pattern in action:
Study the code above and you should be able to tell that we have not
introduced any changes into the main PayPal class. Instead we have created
one interface for our payment adapter and one adapter class for PayPal.
And so afterward we have made the object of the adapter class instead of the
main PayPal class. While creating an object of adapter class we will pass the
object of the main PayPal class as an argument, so that adapter class can
have a reference to the main class and it can call the required methods of the
main PayPal class.
Let's find out how we can utilize this method directly:
Now imagine PayPal changes its method name from sendPayment to
payAmount. Then we just need to make changes in paypalAdapter. Just have a
look at the revised adapter code, which has just one change.
So just one change and we are there.
Adding a New Adapter
At this point, we've seen how we can use the adapter design patten to
overcome the aforementioned scenarios. Now, it's very easy to add a new
class dependent on the existing adapter. Let's say the MoneyBooker API is
there for payment.
Then instead of using the MoneyBooker class directly, we should be applying
the same adapter pattern we just used for PayPal.
As you can see, the same principles apply. You define a method that's
available to third-party classes and then, if a dependency changes its API, you
simply change the dependent class without exposing its external interface.
Conclusion
A great application is constantly hooked into other libraries and APIs, so I
would propose that we implement the adapter method, so that we do not
experience any trouble when a third-party API or library changes its code
base.
I have tried my best to provide an elementary and yet useful example to
demonstrate the adapter design pattern, but if you have additional comments
or questions, please don't hesitate to add them in the feed below.
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Avinash Zala
Avinash is a coder with over six years of experience in web development. With a strong focus on quality and usability, he is interested in delivering cutting edge applications. He is ready to work on responsive applications targeted to various devices. He graduated with a bachelor degree in Information Technology. If you'd like to stay up to date on his activities, refer to his blog or follow him on Twitter and Facebook.
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<?php class PayPal {
public function __construct() { // Your Code here // }
public function sendPayment($amount) { // Paying via Paypal // echo "Paying via PayPal: ". $amount; } }
$paypal = new PayPal(); $paypal->sendPayment('2629');
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
// Concrete Implementation of PayPal Class class PayPal {
public function __construct() { // Your Code here // }
public function sendPayment($amount) { // Paying via Paypal // echo "Paying via PayPal: ". $amount; } }
// Simple Interface for each Adapter we create interface paymentAdapter { public function pay($amount); }
class paypalAdapter implements paymentAdapter {
private $paypal;
public function __construct(PayPal $paypal) { $this->paypal = $paypal; }
public function pay($amount) { $this->paypal->sendPayment($amount); } }
1 2 3
// Client Code $paypal = new paypalAdapter(new PayPal()); $paypal->pay('2629');
01 02 03 04 05 06 07 08 09 10 11 12
class paypalAdapter implements paymentAdapter {
private $paypal;
public function __construct(PayPal $paypal) { $this->paypal = $paypal; }
public function pay($amount) { $this->paypal->payAmount($amount); } }
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
// Concrete Implementation of MoneyBooker Class class MoneyBooker {
public function __construct() { // Your Code here // }
public function doPayment($amount) { // Paying via MoneyBooker // echo "Paying via MoneyBooker: ". $amount; } }
// MoneyBooker Adapter class moneybookerAdapter implements paymentAdapter {
private $moneybooker;
public function __construct(MoneyBooker $moneybooker) { $this->moneybooker = $moneybooker; }
public function pay($amount) { $this->moneybooker->doPayment($amount); } }
// Client Code $moneybooker = new moneybookerAdapter(new MoneyBooker()); $moneybooker->pay('2629');
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Design Patterns The Adapter Pattern
Course: Human Computer Interaction (HCI 308)
University: Kenyatta University
