为了延长我的NSManagedObject
子类的一些功能,我已经定义了一系列协议:雨燕2.0:协议扩展类方法返回自
protocol ManagedObjectFindable {
static func find(format:String, arguments: [AnyObject]?, inContext context:NSManagedObjectContext, entityName:String?) -> Self?
}
protocol UniquelyIdentifiable: ManagedObjectFindable {
var identifier: NSNumber? { get }
static func findWithIdentifier(identifier: Int, inContext context:NSManagedObjectContext) -> Self?
}
所以后来每NSManagedObject
有标识在其数据模型实体可以符合UniquelyIdentifiable
。
为了这个目的,我利用雨燕2.0协议扩展,其中:
extension UniquelyIdentifiable {
static func findWithIdentifier(identifier: Int, inContext context:NSManagedObjectContext) -> Self? {
return self.find("identifier == %lld", arguments: [NSNumber(longLong: Int64(identifier))], inContext: context, entityName:nil)
}
}
在哪里找到的定义为:
extension NSManagedObject: ManagedObjectFindable {
/** returns single entity if found, nil otherwise */
class func find(format:String, arguments: [AnyObject]?, inContext context:NSManagedObjectContext, entityName:String? = nil) -> Self? {
let objectEntityName:String
if let name = entityName {
objectEntityName = name
} else {
objectEntityName = String(self)
}
let fetchRequest = NSFetchRequest()
fetchRequest.entity = NSEntityDescription.entityForName(objectEntityName, inManagedObjectContext: context)
fetchRequest.fetchLimit = 1
fetchRequest.predicate = NSPredicate(format: format, argumentArray: arguments)
var persistentEntityº:NSManagedObject?
context.performBlockAndWait {
do {
let fetchResults = try context.executeFetchRequest(fetchRequest)
if (fetchResults.count != 0){
persistentEntityº = fetchResults.first as? NSManagedObject
}
} catch {}
}
if let persistentEntity = persistentEntityº {
return _safeObjectSelfCast(persistentEntity)
} else {
return nil
}
}
}
func _unsafeObjectSelfCast<T>(obj: AnyObject!) -> T { return obj as! T }
func _safeObjectSelfCast<T>(obj: AnyObject) -> T? { return obj as? T }
现在这些方法返回正确的自我?和编译器的编码时间沉默,但是当编译它给我的错误Method 'findWithIdentifier(_:inContext:)' in non-final class must return 'Self' to conform to protocol 'UniquelyIdentifiable'
现在的事情是,如果不是实施这种方法的协议扩展,我只想致以NSManagedObject
子类,它会去罚款,但是当你在几十个子类中完全复制相同的代码时,这会破坏协议扩展的目的。
任何解决方法,或者我真的错过了什么?
你的代码没有错误编译在我的Xcode 7.1.1 –
@MartinR:尝试添加到NSMOSubclass: 扩展SomeManagedObjectSubclass:UniquelyIdentifiable {} 在这种情况下,它不会...... – ambientlight