iOS - Swift：如何为这种情况编写泛型函数？

Question

我在我的应用程序中使用CoreData。数据库中有4个表格：用户，医学，时间表和患者。对于每一个表，我需要写一个Add函数将数据添加到数据库这样的：

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...

我想写这样一个泛型函数：

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，所以我可以将它与DATA进行比较。或者有没有更好的方法来做到这一点？

Answer 1

对于这种情况下的速度最快的解决方案，因为每个Entity具有不同save实施方式中，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功能使用该协议作为通用参数

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) 
} 

Parameters在这种情况下，应该是一个struct例如，或字典，它完全取决于你