Decorators In C

Turns out you can also do decorators in C, this came in handy for something else I had to work on recently. It’s not quite as nice, because functions aren’t first-class, but handy nonetheless.

Here’s what that looks like:

The output of which is:

vilimpoc@funky:~$ ./c-decorators
hello, C decorators!
functionOne: 1, 2
decorator precondition!
functionOne: 1, 2
decorator precondition!
functionTwo: 1, 2
decorator precondition!
functionThree: 1, 2

This might be a bit simplistic, in reality, you’d probably want to decorate a function with a signature like the following, so that you can just change the structure and not bother w/a bajillion function declarations:

Again, not super elegant, but handy.

Javascript Decorators

One reason why Javascript rocks:

As a use case, imagine you want to restrict a certain set of functions to only run if you are logged in. Doing stuff like this is ridiculously easy with first-class functions.

Here’s a generic decoration example:

Update: Here’s the specific way you’d do this with node.js/Express:

Since all of the URL handlers you register have the same signature, it’s easy to add precondition checks to the handlers via decorators.

You get preconditions essentially for free, which is a damn sight better than adding the if() block to each and every handler function. Also, if you need more preconditions in the future, you can just stack them.