How to sort an array using sort()

Swift version: 5.10

Paul Hudson    @twostraws    June 1st 2019

All arrays have built-in sort() and sorted() methods that can be used to sort the array, but they are subtly different.

If the array is simple you can just call sort() directly, like this, to sort an array in place:

var names = ["Jemima", "Peter", "David", "Kelly", "Isabella"]
names.sort()

If you have a custom struct or class and want to sort them arbitrarily, you should call sort() using a trailing closure that sorts on a field you specify. Here's an example using an array of custom structs that sorts on a particular property:

struct User {
    var firstName: String
}

var users = [
    User(firstName: "Jemima"),
    User(firstName: "Peter"),
    User(firstName: "David"),
    User(firstName: "Kelly"),
    User(firstName: "Isabella")
]

users.sort {
    $0.firstName < $1.firstName
}

If you want to return a sorted array rather than sort it in place, use sorted() like this:

let sortedUsers = users.sorted {
    $0.firstName < $1.firstName
}

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