Programming languages come and go at a frightening clip. Less often but still with some regularity, frameworks appear and disappear as well.
But it’s more infrequent that entire approaches to coding come along. Functional programming has been around forever. Object-oriented programming has been around nearly as long. But it’s only been a little more than a decade that the idea of <em>aspect-oriented programming</em>, or AOP, has been on the scene.
If you’re not familiar with AOP, some background might be helpful. A key idea behind AOP is that there are functions that your code needs to do which go across (or cross-cut) the entire application. In other paradigms, you then need to code bits of those functions all over the place. But in AOP, you do it only once.
One prototypical example is logging. If you’re writing an application that does anything significant, you probably write out to some kind of log when it happens. In a user-based application, for instance, you probably want to log every time you add a new user or delete a user.
Under other approaches, you need to call some kind of logging hook in your addUser and deleteUser functions (or methods). But with AOP, you can define a separate logging function, and tell it to attach to the deleteUser and addUser functions. The parts of the code that actually do the work with users aren’t touched at all.
Why is this helpful? Well, suppose you want to change how logging works or how you call the logging piece. You’d need to touch every place it’s called. With AOP, you just change the logging piece once, and you’re done.
Or suppose you decide well after the design stage that you want to add a layer of security to every user routine to make sure the person trying to make a change has permissions to do so. You could go find all of the functions and add calls to them, or you could just create a security-check routine and attach it to the relevant functions.
Compiled languages like Java and C++ have had this idea for a while now, but it has been slow to come to interpreted languages. With the Flow framework, for instance, PHP now has AOP capabilities. There’s still some roughness around the edges, but it’s a big step toward widespread adoption of this approach.
Watch this space…