How to conform to the Comparable protocol
Swift version: 5.6
The Comparable protocol allows use to use the <, >, <=, and >= operators with conforming data types, which in turn means that Swift knows how to sort arrays of those types. Most of Swift’s built-in types support Comparable out of the box, but if you want your own type to conform to them then you need to implement < – from that Swift can provide default implementations of the other three operators.
The < function needs to accept two instances of your type, one of the left-hand side and one on the right, and return true if the left-hand object should be ordered before the right-hand object.
As an example, consider this simple Person struct:
struct Person {
var name: String
}That has one property called name, and we’re going to make Person conform to the Comparable protocol based on that property. This means writing a static method called < that takes two instances of Person and internally compares the name properties of each of them:
struct Person: Comparable {
var name: String
static func <(lhs: Person, rhs: Person) -> Bool {
return lhs.name < rhs.name
}
}With that in place you can now use < to compare two instances of Person like this:
let taylor = Person(name: "Taylor Swift")
let justin = Person(name: "Justin Bieber")
print(taylor < justin)
SPONSORED Join a FREE crash course for mid/senior iOS devs who want to achieve an expert level of technical and practical skills – it’s the fast track to being a complete senior developer! Hurry up because it'll be available only until October 1st.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 8.0
Similar solutions…
- How to conform to the Hashable protocol
- How to conform to the Equatable protocol
- How to fix “Referencing initializer 'init(wrappedValue:)' on 'ObservedObject' requires that ‘SomeType’ conform to 'ObservableObject'"
- How to fix “Initializer 'init(_:rowContent:)' requires that ‘SomeType’ conform to 'Identifiable’”
- How to constrain a protocol associated type
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
