How to conform to the Equatable protocol

Paul Hudson    October 26th 2018    @twostraws

The Equatable protocol is what allows two objects to be compared using ==, and it’s surprisingly easy to implement because Swift does most of the work for you by default.

First, here’s a struct we can work with:

struct Person {
    var name: String
    var age: String
}

To make that Equatable you need to add the Equatable conformance like this:

struct Person: Equatable {
    var name: String
    var age: String
}

If you don’t want to check all properties for equality, or if any of your properties are not also Equatable, then you need to write your own == function like this:

static func ==(lhs: Person, rhs: Person) -> Bool {
    return lhs.name == rhs.name && lhs.age == rhs.age
}

Put that inside the Person struct. Because that’s your own function you can make it do any comparisons you like. Swift’s default Equatable implementation will check all properties for equality, so if you have one property that is guaranteed to be unique adding your own Equatable implementation is a good idea.

Available from iOS 8.0 – learn more in my book Pro Swift

Did this solution work for you? Please pass it on!

Tweet

Other people are reading…

• What is a singleton?
• How to add associated values to enums
• Checking all array elements match a condition: allSatisfy()
• How to use ISO-8601 dates with JSONDecoder and Codable
• What is an escaping closure?

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.