swift - 如何注入(inject)关联类型的协议(protocol)？

Question

我创建了一个协议(protocol)

protocol DataBaseManager{
    associatedtype type
    init()
    func insert(object obj: [type])
    func getObject(ofType type: type.Type)-> Array<type>
    //...

}

现在我将 RealmManager 定义为

class RealmManager: DataBaseManager{

    var realm:Realm!

    required init() {
        do{
            realm =  try Realm()
        }catch {
            print(error)
        }
    }

    func insert(object obj: [Object]) {
        do {
            try realm.write {
                realm.add(obj)
            }
        } catch let error {
            print("the error in creation of object is \(error)")
        }
    }

    func getObject(ofType type: Object.Type)-> Array<Object> {
        let objects = realm.objects(type)
        return Array(objects)
    }
    //.....
}

这样做的全部目的是在必要时轻松替换数据库到 SqliteManager。为此，我将 viewModel 中的依赖项发送为:

  struct LoginViewModel {

    var dbManager:DataBaseManager //error in this line
    init(dbManager: DataBaseManager) {
        //.....
        self.dbManager = dbManager
    }
}

并将其称为

let loginViewModel = LoginViewModel(dbManager:RealmManager())

但是我收到错误

Protocol 'DataBaseManager' can only be used as a generic constraint because it has Self or associated type requirements

因为 swift 不支持注入(inject)关联类型的协议(protocol)。有什么可能的调整来解决这个问题？

Answer 1

尝试为 LoginViewModel 结构提供通用类型参数并使用它:

struct LoginViewModel<DBM: DataBaseManager> {

    var dbManager: DBM

    init(dbManager: DBM) {
        self.dbManager = dbManager
    }
}