Static Var closure returns Type.Type instead of Type - swift

Question

I try to break, count and later join objects inside another class.
So I build protocol:
typealias DataBreaker<T> = () -> [Double]
typealias DataJoiner<T> = (_ particles: [Double]) -> T
protocol SpaceIntepolatable {
associatedtype Atom
var breaker:DataBreaker<Atom> {get}
static var joiner:DataJoiner<Atom> {get}
}
and build an extension for Point:
extension Point:SpaceIntepolatable {
typealias Atom = Point
var breaker:DataBreaker<Atom> {
return {
return [self.x, self.y]
}
}
static var joiner:DataJoiner<Atom> {
return {particles in
return Atom(x: particles[0], y: particles[1])
}
}
}
Till now is fine. I can break Point into an Array<Double>
let particles = atom.breaker()
but joining
let newAtom = Atom.joiner(particles)
causes a compiler error:
Cannot convert value of type 'Atom.Atom' to specified type 'Atom'
It's probably because joiner is a static. But how to avoid it and get Atom as a result?

Answer 1

You have to call it on Point when you are outside the scope of the class.
let newAtom = Point.joiner(particles)
Edit:
You say that you have a generic class that looks like this:
class Space<Atom: SpaceIntepolatable> {
func test() {
let particles: [Double] = [0, 1]
let newAtom: Atom = Atom.joiner(particles)
}
}
Now, the problem is that the type of newAtom is incorrect. The SpaceIntepolatable protocol doesn't specify that Point and Point.Atom are the same type. Therefore Atom (Point) and Atom.Atom (Point.Atom) are not considered the same. What we want is Atom.Atom. Or we can just let the type to be inferred:
let newAtom: Atom.Atom = Atom.joiner(particles)
let newAtom = Atom.joiner(particles)
In general it is advisable not to reuse type names because then you get things like Atom.Atom. Maybe you actually want something like this:
protocol SpaceIntepolatable {
var breaker: DataBreaker<Self> { get }
static var joiner: DataJoiner<Self> { get }
}
and lose the Atom typealias completely, then:
class Space<Atom: SpaceIntepolatable> {
func test() {
let particles: [Double] = [0, 1]
let newAtom: Atom = Atom.joiner(particles)
}
}
will actually work.