iOS

Question

我在我的应用程序中使用了 CoreData。数据库中有 4 tables：User、Medicine、Schedule 和 Patient。对于每个 table 我需要编写一个添加函数来将数据添加到数据库中，如下所示：

func addUser(email: String, password: NSData, handler: @escaping (_ status: SaveStatus, _ error: NSError?) -> Void){
    let managedContext = (UIApplication.shared.delegate as? AppDelegate)?.managedObjectContext
    let entity = NSEntityDescription.entity(forEntityName: DB.TABLE.USER, in: managedContext!)!
    let nurse = NSManagedObject(entity: entity, insertInto: managedContext) as! User
    nurse.email = email
    nurse.password = password

    save { (status, error) in
        handler(status, error)
    }
}

func addMedicine(name: String, handler: @escaping(_ status: SaveStatus, _ error: NSError?) -> Void){
    let managedContext = (UIApplication.shared.delegate as? AppDelegate)?.managedObjectContext
    let entity = NSEntityDescription.entity(forEntityName: DB.TABLE.MEDICINE, in: managedContext!)!
    let medicine = NSManagedObject(entity: entity, insertInto: managedContext) as! Medicine
    medicine.name = name

    save { (status, error) in
        handler(status, error)
    }
}

等等...

我想写一个像这样的通用函数：

func addDataToDB<DATA>(object: DATA, handler: @escaping SaveStatusHandler){
    switch DATA {
    case DATA is LoginData:
        break
    default:
        break
    }
}

我不知道LoginData应该是什么类型，所以我可以用它来比较DATA。或者有更好的方法吗？

Answer 1

由于每个 Entity 都有不同的 save 实现，这种情况下最快的解决方案是声明一个 Saveable 协议

protocol Saveable {
    associatedtype Parameters
    static var entityName: String { get }
    static var context: NSManagedContext { get }
    func setup(with parameters: Parameters)
    func save(_ handler: () -> ())
}

然后在addDataToDB函数

中使用这个协议作为泛型参数

func addDataToDB<T>(params: T.Parameters, _ handler: () -> ()) where T: Saveable {
    let entity = NSEntityDescription.entity(forEntityName: T.entityName, in: T.contenxt)!
    let object = NSManagedObject(entity: entity, insertInto: T.context) as! T
    object.setup(with: params)

    object.save(handler)
}

例如，

Parameters 应该是 struct 或字典，这完全取决于您

iOS - Swift: 如何为这种情况编写泛型函数？

iOS - Swift: How to write generic function for this case?

xcode

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swift3