Negative Thinking

It's a knot. It'll all make sense in a minute, I promise.

You should know me by now, I like to weave a story, set the scene and/or derail a train of thought before it’s left the station.

Anyway, oftentimes when developing we are faced with a teaser that stops us in our tracks, if even ever so briefly. It will be around logical operations and usually the sentence that enters our mind will be something like:

If is not not this, then that
If… not not??
what??

Sound familiar?

This can normally be most prevalent when dealing with collections, where there is a useful isEmpty property available, but that only checks the negative state of that collection - “is this empty?” but it is also likely that we want to make sure that the collection is not empty before executing a section of code.

As such, it’s expected to use the ! prefix before that variable to do an inverse check of that value, however this comes at the expense of legibility and simplicity of scanning the code.

And like I covered in a previous post, one of the things we should be looking to do, in small but frequent steps, is refactoring as we go to improve legibility and as such, I’d like to introduce my latest invention.

Please put your hands together for:

The isNotEmpty variable.

I will hold for rapturous applause for a second..

Code Block

extension Collection {
    var isNotEmpty: Bool {
        return !self.isEmpty
    }
}

And an example:

let items = [1, 2, 3, 4, 5, 6]

if items.isNotEmpty {
	items.removeAll()
}

That’s it. We can now use this instead of !isEmpty on collections to keep our abliity to read and understand the code fast and also reduce the number of logical bugs introduced by misunderstanding or overlooking a stray exclamation mark.

Wrap Up

That’s it really, just a useful little extension on Collection that can be used in place of !isEmpty.
A return to normal programming next month, pinky swear!