How to avoid duplicate initializing when adopting protocol? - swift

Question

I know I can do this with super class, but Swift doesn’t support abstract class, and I wanna use protocol instead. However, when there are many property requirements, I find it really hard to avoid duplicate self.xxx = xxx code.. Example:
protocol ManyProperties {
var a: Int { get }
var b: Int { get }
var c: Int { get }
var d: Int { get }
}
struct S: ManyProperties {
let a: Int
let b: Int
let c: Int
let d: Int
init(a: Int, b: Int, c: Int, d: Int) {
self.a = a
self.b = b
self.c = c
self.d = d
}
}
class C: ManyProperties {
let a: Int
let b: Int
let c: Int
let d: Int
// duplicate initializing
init(a: Int, b: Int, c: Int, d: Int) {
self.a = a
self.b = b
self.c = c
self.d = d
}
}
I really want to type something like super.init() and I do not want inheritance. How can I accomplish this?

Answer 1

Structs has a free memberwise initializer, so you don't need to write this kind of init for them:
struct S: ManyProperties {
let a, b, c, d: Int
}
but for the class you have some options:
1- Use base class and inherit from it instead of conforming to protocol:
class ManyPropertiesClass: ManyProperties {
let a: Int
let b: Int
let c: Int
let d: Int
// duplicate initializing
init(a: Int, b: Int, c: Int, d: Int) {
self.a = a
self.b = b
self.c = c
self.d = d
}
}
class C: ManyPropertiesClass {
}
2- Add init inside the protocol, so it forces you to implement it with a little autocompletion help
protocol ManyProperties: class {
var a: Int { get }
var b: Int { get }
var c: Int { get }
var d: Int { get }
init(a: Int, b: Int, c: Int, d: Int)}
}
3- define another initializer inside the protocol and make variables setable so the compiler knows that all properties are initialized. Then you can extend the protocol to have the initializer:
protocol ManyProperties: class {
var a: Int { get set }
var b: Int { get set }
var c: Int { get set }
var d: Int { get set }
init()
}
extension ManyProperties {
init(a: Int, b: Int, c: Int, d: Int) {
self.init()
self.a = a
self.b = b
self.c = c
self.d = d
}
}
class C: ManyProperties {
var a: Int = 0
var b: Int = 0
var c: Int = 0
var d: Int = 0
required init() {}
}