Inheritable static factory method in Swift class

Question

Consider this static factory method written in Objective-C:

@implementation User

+ (instancetype)named:(NSString *)name {
    let user = [self new];
    user.name = name;
    return user;
}

@end

How do I implement it in Swift? The plenty of Self/self/Type/type keywords in Swift feels fuzzy and I struggle to figure out the right solution.

Answer 1

The solution came out to be like this:

class User {
    var name: String

    required init(name: String) { self.name = name }

    class func named(_ name: String) -> Self {
        let instance = Self.init(name: name)
        return instance
    }
}

The following example shows everything works fine:

class Admin: User {
    override class func named(_ name: String) -> Self {
        let decoratedName = "~\(name)~"
        let instance = Self.init(name: decoratedName)
        return instance
    }

    func ban(user: User) {
        print("User \(user.name) banned by \(name)!")
    }
}

let user = User.named("John")
let admin = Admin.named("Peter")
admin.ban(user: user) // Yields 'User John banned by ~Peter~!'

So, you should pay attention to these keypoints:

• Your class must have a required constructor (maybe even without arguments)
• You should call it on Self. inside your method
• Your method should have class access modifier
• Your method's return type should be -> Self (note the capital S)