attributes-with-defaults.swift

protocol Attributed {
    var attrs: Attrs { get }
}

struct Attrs {
    let name: String
    let sortBy: String
    let keyPath: [String]

    // init has defaults
    init(name: String, sortBy: String, keyPath: [String] = []) {
        self.name = name
        self.sortBy = sortBy
        self.keyPath = keyPath
    }
}

struct SomeAttributed: Attributed {
    let attrs = Attrs(
        name: "some",
        sortBy: "priority",
        keyPath: ["my", "some"]
    )
}

struct OtherAttributed: Attributed {
    // new attributes can be added with defaul value, therefore no need to update all attributed declarations
    let attrs = Attrs(
        name: "other",
        sortBy: "id"
    )
}