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• Comparable for custom types
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Adding conformance to Comparable for custom types

• Swift's default sorting mechanism allows us to sort arrays of basic types effortlessly.
• When dealing with custom types, such as structs, Swift doesn't inherently understand how to compare and sort them.

Example

struct User: Identifiable {
    let id = UUID()
    let firstName: String
    let lastName: String
}

let users = [
    User(firstName: "Arnold", lastName: "Rimmer"),
    User(firstName: "Kristine", lastName: "Kochanski"),
    User(firstName: "David", lastName: "Lister"),
].sorted {
    $0.lastName < $1.lastName
}

Comparable

Comparable | Apple Developer Documentation

Swift provides the Comparable protocol, which allows custom types to define their own sorting behavior.

Example, the User struct represents a user with a first name and a last name.

We want to sort an array of User objects based on their last names.

• Conform to the Comparable protocol
• Define the < operator function, comparing the lastName property of two User instances.
• The lhs parameter represents the left-hand side of the comparison, and rhs represents the right-hand side.
• The function returns true if lhs's last name comes before rhs's last name, ensuring the array is sorted in ascending order of last names.

struct User: Comparable {
    let firstName: String
    let lastName: String
    
    static func < (lhs: User, rhs: User) -> Bool {
        return lhs.lastName < rhs.lastName
    }
}