ios - Swift - 在基类中使用 'Self' 的类型？

Question

我有一个 NSManagedObject 子类 Shop，我在 swift 中为其定义了以下函数:

    // insertions
public class func insertOrUpdateRepresentation(representation: Dictionary<String, AnyObject>, context: NSManagedObjectContext) -> Shop {

    let identifier = representation["id"] as! NSNumber
    let string = identifier.stringValue
    var shop = Shop.fetchObjectWithIdentifier(string, context: context) as! Shop?

    // insert if needed
    if (shop == nil) {
        shop = NSEntityDescription.insertNewObjectForEntityForName(Shop.entityName(), inManagedObjectContext: context) as? Shop
    }

    // update
    shop?.deserializeRepresentation(representation)
    return shop!
}

现在，我想为此对象(和其他对象)定义一个基类，我可以在该方法中使用类类型。现在在 Objective C 中，我可以在这里引用“self”来获取当前调用者的类。

    // insertions
public class func insertOrUpdateRepresentation(representation: Dictionary<String, AnyObject>, context: NSManagedObjectContext) -> MyManagedObject {

    let identifier = representation["id"] as! NSNumber
    let string = identifier.stringValue
    var obj = (class of the caller).fetchObjectWithIdentifier(string, context: context) as! (class of the caller)?

    // insert if needed
    if (obj == nil) {
        obj = NSEntityDescription.insertNewObjectForEntityForName((class of the caller).entityName(), inManagedObjectContext: context) as? (class of the caller)
    }

    // update
    obj?.deserializeRepresentation(representation)
    return obj!
}

如何在 swift 中实现这种功能？

谢谢!

Answer 1

通过使用像这样的 swift Types 来让它工作:

    public class func insertOrUpdateRepresentation<T: DDManagedObject>(representation: Dictionary<String, AnyObject>, context: NSManagedObjectContext, type: T.Type) -> T {

    let identifier = representation["id"] as! NSNumber
    let string = identifier.stringValue
    var obj = T.fetchObjectWithIdentifier(string, context: context) as! T?

    // insert if needed
    if (obj == nil) {
        obj = NSEntityDescription.insertNewObjectForEntityForName(T.entityName(), inManagedObjectContext: context) as? T
    }

    // update
    obj?.deserializeRepresentation(representation)
    return obj!
}