Simplifying the Adapter Pattern: Making Interfaces Interact Seamlessly

TLDR: The Adapter Pattern is a design tool that lets us reconcile discrepancies between different interfaces. This pattern allows different parts of an application to interact without rewriting or refactoring extensive sections of your code. Primarily used during the refactoring process, the Adapter Pattern is ideal for managing changes between dependencies without upending your entire codebase. In this article, we’ll explore this pattern in-depth and learn to implement it through an easy-to-follow example.

The Adapter Pattern is a lifesaver in the complex world of programming. It serves as a bridge, letting one interface interact with another that otherwise wouldn’t be compatible. Think of it as the universal travel adapter that enables your devices to function in a foreign country.

An object’s interface, comprising its methods and properties, is how we interact with that object. But what if we need to change something about this object? It would be a real pain to go through our code and refactor the object, especially if it has numerous dependencies. Here is where the Adapter Pattern comes to the rescue.

Let’s make it crystal clear with an example, shall we?

Step 1 – Our first script is an old email validation script, oldInterface.js. This script checks if a string has an “@” symbol.

define(function () {
    'use strict';

    var OldInterface = function () { }; //set up an object constructor

    OldInterface.prototype.doSomethingOld = function () { //add a method to the constructor prototype
        console.log('doing the old thing');
    };

    return new OldInterface(); //return a new instance of the object
});

Step 2 – We then create a new interface, newInterface.js. It does a similar job but with a little twist – it accepts an argument in its function.

define(function () {
    'use strict';

    var NewInterface = function () { }; //set up an object constructor

    NewInterface.prototype.doSomethingNew = function (newArg) { //add a method to the constructor prototype
        console.log('doing the ', newArg);
    };

    return new NewInterface(); //return a new instance of the object
});

Step 3 – Here comes our hero, adapter.js. This script acts as a bridge, making our old interface work seamlessly with the new one without any refactoring.

define(function (require) {
    'use strict';

    var newInterface = require('adapter/newInterface'); //require in the new interface

    return {
        doSomethingOld: function () { //reset the method from the oldInterface with the method from the new interface
            return newInterface.doSomethingNew('new thing');  
        }
    };
});

Step 4 – We initialize our Adapter, init.js.

define(function(require) {
    'use strict';

    return {
        init: function() {

            var OldInterfaceAdapter = require('adapter/adapter'); //set up new variable for OldInterface and rename to OldInterfaceAdapter to make it clear to any subsequent coders that we are using an adapter for the oldInterface

            OldInterfaceAdapter.doSomethingOld();
        }
    };
});

Step 5 – Lastly, we put everything together in main.js.

// JavaScript Document
require (
    ['adapter/init'],
    function (adapter) {
        'use strict';

        var examples = {

            adapter:adapter
        };

        window.runExample = function (example) {
            examples[example].init();
        };
    }
);

Conclusion

The Adapter Pattern is a design pattern that shines when changes are needed between dependencies. It isn’t typically a go-to during initial application development but becomes a powerful tool when refactoring code to make things work better and more efficiently. The Adapter Pattern allows us to modify one part of our application without disrupting the rest, ensuring that our software remains robust, flexible, and easier to maintain. So, the next time you encounter a change that could mess up your whole codebase, remember, the Adapter Pattern might just be the answer.