CoreData 插入新数据，保留现有数据

Question

我从 Web 服务获取数据，然后将其存储在 Core Data 中。当我从 Web 服务获取新数据时，它包含我已经存储的数据。在 Core Data 中，我存储了 Web 服务提供的每个数据集的唯一 ID。在我当前的实现中，我只存储具有唯一 ID 的集合的多个实例。但我希望保留现有的，而忽略新的。或者，因为它们无论如何都是相同的，所以新的将覆盖现有的。这里的方法是什么？

谢谢

Answer 1

class func defaultInsert(data:[String:Any]) -> AppLabels {
    var label = self.fetchLabelFromLabelUsingVarID(var_id: data["var_id"] as! String,screen: data["name"] as! String)
    if label == nil{
        label = NSEntityDescription.insertNewObject(forEntityName: "AppLabels", into: CoreDataStack.managedObjectContext) as? AppLabels
    }
    if data["var_id"] != nil {
        label?.var_id = data["var_id"] as? String
    }
    if data["name"] != nil {
        label?.name = data["name"] as? String
    }
    if data["value"] != nil {
        label?.value = data["value"] as? String
    }
    if data["var_name"] != nil {
        label?.var_name = data["var_name"] as? String
    }

    return label!;
}
 class func fetchLabelFromLabelUsingVarID (var_id:String,screen:String) -> AppLabels? {
    let fetchrequest = NSFetchRequest<AppLabels>(entityName: "AppLabels")
    fetchrequest.predicate = NSPredicate(format: "var_id == %@ && name == %@", var_id,screen);
    fetchrequest.fetchLimit = 1;
    do {
        let fetchedResults = try CoreDataStack.managedObjectContext.fetch(fetchrequest)
        if let applabel = fetchedResults.first {
            return applabel
        }
    }
    catch{

    }
    return nil;
}

Answer 2

首先，您必须使用 uniqID 检查数据库中是否存在来自 API 的新对象。如果是，则将旧对象覆盖为新对象，如果无法获取，则插入一个新对象。

按照示例代码可能对您有所帮助

    //MARK:- get if ClassRoom Exist
    func getClassroom(_ classRooMID:String) -> Classroom? {

        var allClassroom:[Classroom]!
        let request = Classroom.getFetchRequest()
        let keyVal = classRooMID
        request.predicate = NSPredicate.init(format: "classroomid = %@", argumentArray: [keyVal])
        do {
            allClassroom = try managedObjectContext.fetch(request) as! [Classroom]
        }
        catch let error as NSError{
            // failure
            print("Fetch failed: \(error.localizedDescription)")
        }
        if allClassroom.count != 0 {
            return allClassroom[0]
        }
        return nil
    }

插入新对象时

    //MARK:- InsertClassroom Data
    func insertClassroomData(_ classRoomDict:NSDictionary) -> Classroom {
        let keyValue = classRoomDict[KEY_CLASS_ROOM_ID] as! String
        var classroomObj = self.getClassroom(keyValue)

        if (classroomObj == nil){
            classroomObj = NSEntityDescription.insertNewObject(forEntityName: "Classroom", into: managedObjectContext) as? Classroom
        }
        classroomObj!.setClassroomFromDict(classRoomDict)

        return classroomObj!
    }

谢谢

CoreData 插入新数据，保留现有数据

CoreData insert new data, leave existing

core-data

overwrite

ios