Override same var name

Override.swift

protocol BodyParameters { }
struct JSONBodyParameters: BodyParameters { }
struct MultipartFormDataBodyParameters: BodyParameters { }

protocol Request {
    var bodyParameters: BodyParameters? { get }
}

extension Request {
    var bodyParameters: BodyParameters? {
        return nil
    }
}

struct Request1: Request {
    let bodyParameters: JSONBodyParameters?

    init() {
        self.bodyParameters = JSONBodyParameters()
    }
}

struct Request2: Request {
    let bodyParameters: BodyParameters?

    init() {
        self.bodyParameters = JSONBodyParameters()
    }
}


let request1 = Request1()
request1.bodyParameters // JSONBodyParameters
(request1 as Request).bodyParameters // nil


let request2 = Request2()
request2.bodyParameters // JSONBodyParameters
(request2 as Request).bodyParameters // JSONBodyParameters