CODEWITHSUNDEEP
swift
Patrick Kelly
Patrick Kelly

Reputation: 145

Swift - class and func keyword

What exactly does it mean for a function to be defined this way:

class Foo {
    private class func bar() {
         //do something cool
    }
}

In other words, what is the purpose of the second class keyword here?

Using Swift 2.1.

Upvotes: 3

Views: 703

Answers (3)

Lachlan Roche
Lachlan Roche

Reputation: 25966

class and static methods are invoked via the type, rather than on instances. 

let x = NSString.pathWithComponents(["/", "usr", "local", "bin", "brew"])

Any type can have static methods, class methods may only occur on classes. Subclasses can override class methods but not static ones.

class Foo {
    class func bar() -> String {
        return "foo bar"
    }
    static func baz() -> String {
        return "foo baz"
    }
}
class Bar: Foo {
    override class func bar() -> String {
        return "bar bar"
    }
}

Upvotes: 6

Leo Correa
Leo Correa

Reputation: 19839

It simply declares the function on the class itself rather than an instance of the class.

class Foo {
    private class func omg() -> String {
        return "OMG"
    }
}

Foo.omg() => "OMG"

calling 

let f = Foo()

f.omg() => Static member 'omg' cannot be used on instance of type 'Foo'

So you can see the difference

Upvotes: 3

Michał Banasiak
Michał Banasiak

Reputation: 960

it is a class function, so you can call it on a class, no class instances. it is the same as static in java/c++

class A {
    public class func f() {
        print("hey")
    }
}

A.f()

Upvotes: 1

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