How to sort structures by property in Swift

Question

I am trying to sort an array of structure depending on its property.

Lets say I want to sort an array of NSViews by the x coordinate.

How can I achive this?

Answer 1

Its a very pretty solution for that, and its called Closure Expression Syntax.

What you need to do is:

let sortedArray = sorted(allViewsArray, { (p1: NSView, p2: NSView) -> Bool in
            return p1.frame.origin.x < p2.frame.origin.x
        })

This will sort the alLViewsArray from the biggest X coordinate to the smallest, and store it in sortedArary.

Answer 2

Note, you can simplify the syntax a little, which often helps with readability (focus is on what you’re doing rather than the syntax of the types etc):

let sortedArray = sorted(allViewsArray) {
    $0.frame.origin.x < $1.frame.origin.x
}

Trailing closures can be outside the function call parens, resembling other block structures like if or while; you can skip the return if the closure expression is a single statement, and you can skip the function signature and use $0, $1 etc. for the argument names.

That last one is best used only when there are no more useful names to be had (e.g. p1 is no more descriptive than $0). If you do want to give them names, you can still skip the types:

let sortedArray = sorted(allViewsArray) { p1, p2 in
    p1.frame.origin.x < p2.frame.origin.x
}

Swift is sometimes a little fragile when applying this syntax sugar so occasionally you’ll find it can’t be shortened quite as much as it ought, but it usually works.