Ios 如何创建面向协议的通用服务？

我正在尝试创建一个协议，为视图控制器提供数据。我试图采用协议方法，使事情变得灵活，这样视图控制器就可以使用任何类型的数据进行协调

但是，我得到了一个错误：

协议“可服务”只能用作一般约束，因为它具有自身或关联的类型要求

这就是我想做的：

protocol Serviceable {
    associatedtype DataType
    func get(handler: ([DataType] -> Void)?)
}

struct PostService: Serviceable {
    func get(handler: ([Postable] -> Void)? = nil) {
        print("Do something...")
    }
}

struct AuthorService: Serviceable {
    func get(handler: ([Authorable] -> Void)? = nil) {
        print("Do something...")
    }
}

protocol Postable {
    var title: String { get set }
    var content: String { get set }
}

protocol ServiceControllable: class {
    var service: Serviceable { get } // Error: Protocol 'Serviceable' can only be used as a generic contraint because it has Self or associated type requirements
}

extension ServiceControllable {
    func setupDataSource() {
        service.get { items in
            // Do something
        }
    }
}

class MyViewController: ServiceControllable {
    let service: Serviceable = PostService() // Error: Same as above

    override func viewDidLoad() {
        super.viewDidLoad()
        setupDataSource()
    }
}

---

我如何设置它，以便我的视图控制器能够实现ServiceControlable，并能够访问填充表、集合等的通用setupDataSource？

您想要这样的东西

import UIKit

protocol Serviceable {
    associatedtype DataType
    func get(handler: ([DataType] -> Void)?)
}

struct PostService: Serviceable {
    func get(handler: ([Postable] -> Void)? = nil) {
        print("Do something...")
    }
}

protocol Authorable {}

struct AuthorService: Serviceable {
    func get(handler: ([Authorable] -> Void)? = nil) {
        print("Do something...")
    }
}

protocol Postable {
    var title: String { get set }
    var content: String { get set }
}

protocol ServiceControllable: class {

    // THIS is the way to use generic-constraint-protocols in protocols.
    associatedtype _Serviceable: Serviceable

    var service: _Serviceable { get }

}

extension ServiceControllable {
    func setupDataSource() {
        service.get { items in
            // Do something
        }
    }
}

class MyViewController: UIViewController, ServiceControllable {

    let service = PostService()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupDataSource()
    }
}

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