我有一个一对多的关系,看起来像这样,
我已经在一个文件中设置了我的模型类来匹配:
import CoreData
import Foundation
class Board: NSManagedObject {
@NSManaged var boardColor: String
@NSManaged var boardCustomBackground: AnyObject?
@NSManaged var boardID: String
@NSManaged var boardName: String
@NSManaged var lists: NSSet
}
class List: NSManagedObject {
@NSManaged var listID: String
@NSManaged var listName: String
@NSManaged var board: Board
}
因为我要从多个JSON端点获取数据,所以我必须将列表与主板分开保存。我想做的是为具有匹配的boardID的线路板创建/更新列表。
这是我在多次尝试之后的情况:
func saveList(boardID: String, listName: String, listID: String) {
let request = NSFetchRequest(entityName: "Board")
var error: NSError? = nil
request.predicate = NSPredicate(format: "boardID like %@", boardID)
let results: NSArray = context.executeFetchRequest(request, error: &error)
if results.count > 0 {
for result in results {
let board = result as Board
let list = NSEntityDescription.insertNewObjectForEntityForName("List", inManagedObjectContext: context) as List
println(" want to save \(listName) in \(board.boardName)")
board.lists.addListObject(lists)
list.listName = listName
list.listID = listID
}
}
}
基于Defining CoreData Relationships in Swift和this,我尝试实现了@Keenle对在板内定义列表对象的回答:
import Foundation
extension Board {
func addListObject(value:List) {
var items = self.mutableSetValueForKey("lists");
items.addObject(value)
}
func removeListObject(value:List) {
var items = self.mutableSetValueForKey("lists");
items.removeObject(value)
}
}
但是,我在board.lists.addListObject(lists)
遇到了以下错误:'NSSet‘没有名为'addListObject'`的成员
我也尝试了board.lists.listName = listName
,而不是board.lists.addListObject(lists)
,就像这个Obj-C example中所暗示的那样,但遗憾的是,这也不起作用。
(此外,println
输出正确指定了正确的电路板和列表。)
提前感谢!
发布于 2014-08-05 05:09:06
在一对多关系中,更容易设置反向关系的“一对一”方向,在本例中只需
list.board = board
因此,这里实际上不需要扩展方法。
发布于 2014-08-05 04:48:09
您应该在board
对象上调用addListObject(...)
:
board.addListObject(list) // notice that we pass just one object
另外,如果您希望能够向特定board
对象添加一组列表,则可以使用接受对象集方法来增强Board
类扩展:
func addList(values: NSSet) {
var items = self.mutableSetValueForKey("lists");
for value in values {
items.addObject(value)
}
}
func removeList(values: NSSet) {
var items = self.mutableSetValueForKey("lists");
for value in values {
items.removeObject(value)
}
}
发布于 2016-01-31 00:22:19
如果您定义:
@NSManaged var lists: Set<List>
然后您可以执行以下操作:
board.lists.insert(list)
https://stackoverflow.com/questions/25127090
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