Can't conform Array to same protocol twice?

Using Swift
1

There's no way to do something like this, correct?

protocol NodePathProtocol { ... }
typealias IDNodePath = [UUID]
typealias IntNodePath = [Int]
extension IntNodePath: NodePathProtocol { ... }
extension IDNodePath: NodePathProtocol { ... }

I guess I'll just change the code to make my types structs, like:

struct IntNodePath {
    val path: [Int] 
}
2

Correct.

1 Like
3

A different workaround is to add a separate protocol for the array elements, and a conditional conformance on Array that uses the element-specific protocol:

import Foundation

protocol NodePathProtocol {
    var components: [String] { get }
}

protocol NodePathArrayElementProtocol {
    static func nodePathComponents(for array: [Self]) -> [String]
}

extension Array: NodePathProtocol where Element: NodePathArrayElementProtocol {
    var components: [String] { Element.nodePathComponents(for: self) }
}

extension Int: NodePathArrayElementProtocol {
    static func nodePathComponents(for array: [Int]) -> [String] {
        return array.map { String($0) }
    }
} 

extension UUID: NodePathArrayElementProtocol {
    static func nodePathComponents(for array: [UUID]) -> [String] {
        return array.map { $0.uuidString }
    }
}
4

Such use case could possibly be enabled with [Pitch] Extensions on bound generic types.

And you still cannot conforming Array to the same protocol by such declarations. Instead, you may conditionally conform different concrete types specialized with Array to the protocol.