How do I implement this protocol in struct

Question

I'm new to Swift and I want to create an abstract factory for db access. Here is my protocol

protocol IDAOFactory
{
  associatedtype DAO: IDAO

  func createAccountDAO<DAO: IAccountDAO>() -> DAO
}

struct RealmFactory: IDAOFactory
{

}

protocol IDAO
{
   associatedtype T
   func save(object: T)
}

protocol IAccountDAO : IDAO
{

}

struct AccountDAORealm: IAccountDAO
{

}

How to implement the IDAOFactory in struct RealmFactory and IAccountDAO in struct AccountDAORealm? Can anybody help?

Answer 1

Swift中的泛型具有许多限制，特别是在协议中使用并在struct中实现时。让我们等到Swift 3：）

我使用协议和派生类或泛型与类，但混合协议泛型和结构在Swift 2（C＃泛型更方便）中令人头疼

我在游乐场玩你的代码，这里是

protocol IDAOFactory
{
    associatedtype DAO: IDAO

    func createAccountDAO<DAO: IAccountDAO>() -> DAO
}

protocol IDAO
{
    init()
    associatedtype T
    func save(object: T)
}

protocol IAccountDAO : IDAO
{
    init()
}

public class AccountDAORealm: IAccountDAO
{
    var data: String = ""

    required public init() {
        data = "data"
    }

    func save(object: AccountDAORealm) {
        //do save
    }
}

let accountDAORealm = AccountDAORealm() 
//As you see accountDAORealm is constructed without any error

struct RealmFactory: IDAOFactory
{
    func createAccountDAO<AccountDAORealm>() -> AccountDAORealm {
        return  AccountDAORealm() //but here constructor gives error
    }
}