Written by Paul Hudson @twostraws
The Equatable
protocol is what allows two objects to be compared using ==
, and it’s surprisingly easy to implement. In fact, if you’re using Swift 4.1 or later and meet certain criteria, it’s trivial to implement!
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’re using Swift 4.1 or later, and have no special requirements, that’s your code complete – Swift can take care of the rest.
If you’re on an earlier version of Swift, if you don’t just 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
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