You can think of many concerns that'll cut your app like caching, analytics, security. Why are Cross Cutting Concerns bad ?
- Single Responsibility Principle is violated. Example: You have a network module that also logs, secures, sends analytics etc.
- It breaks the modularity of your app.
- It makes the code practically not reusable. Business logic should be separated from implementation code.
Decorator Pattern
How do we fix this ? There has to be some pattern, right ? Well, there is. You can use the Decorator pattern to decorate the operation with all the concerns.Here's a lengthy post about having abstracted commands, that can be decorated.
Of course, there's a drawback to all that: a lot of abstractions. Of course, abstracting your modules in your code is good, but this forces you to abstract every little action you want to log (for example). You can end up with hundreds of interfaces, just for the sake of removing cross cutting concerns. Quite costly, huh ? There has to be a better way.
Aspect Oriented Programming
Wikipedia for Aspect Oriented Programming might look a little scary, but it can be as simple as that: you set up blocks of code to be executed before, or after a certain method in a certain class.
The Aspects library for Objective-C uses method swizzling to achieve that. Very clean, doesn't need additional classes/abstractions, it isolates your concerns.
