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swiftstaticswift3swift-protocols
cfischer
cfischer

Reputation: 24892

Static keyword in Swift 3 protocol

I noticed that some functions in Swift protocols have the static keyword. However, when you implement the function, you must remove the static keyword to make the compiler happy.

public static func <(lhs: Self, rhs: Self) -> Bool

What does static mean in the context and what is its purpose?

Upvotes: 1

Views: 1764

Answers (2)

Ashish
Ashish

Reputation: 116

Static properties and methods

Swift lets you create properties and methods that belong to a type, rather than to instances of a type. This is helpful for organizing your data meaningfully by storing shared data.

Swift calls these shared properties "static properties", and you create one just by using the static keyword. Once that's done, you access the property by using the full name of the type. Here's a simple example:

struct TaylorFan {

    static var favoriteSong = "Shake it Off"
    var name: String
    var age: Int
}

let fan = TaylorFan(name: "James", age: 25)

print(TaylorFan.favoriteSong)

So, a Taylor Swift fan has a name and age that belongs to them, but they all have the same favorite song.

Because static methods belong to the class rather than to instances of a class, you can't use it to access any non-static properties from the class.

Upvotes: 2

vadian
vadian

Reputation: 285039

From the Xcode 8 beta 4 release notes:

Operators can be defined within types or extensions thereof. For example:

struct Foo: Equatable {
    let value: Int
    static func ==(lhs: Foo, rhs: Foo) -> Bool {
        return lhs.value == rhs.value
    }
}

Such operators must be declared as static (or, within a class, class final), and have the same signature as their global counterparts. As part of this change, operator requirements declared in protocols must also be explicitly declared static:

protocol Equatable {
    static func ==(lhs: Self, rhs: Self) -> Bool
}

Upvotes: 4

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