[英]Saving CoreData to-many relationships in Swift
I have a one-to-many relationship that looks like so, 我有一对多的关系,看起来像这样,
I've set up my model classes in a file to match: 我在一个文件中设置我的模型类来匹配:
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
}
Because I'm fetching data from multiple JSON endpoints, I have to save my lists seperately from my boards. 因为我从多个JSON端点获取数据,所以我必须单独从我的板上保存我的列表。 What I want to do is create/update a list for a board with a matching boardID .
我想要做的是为具有匹配boardID的电路板创建/更新列表 。
Here's where I am after multiple attempts: 这是我经过多次尝试的地方:
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
}
}
}
Based on Defining CoreData Relationships in Swift and this , I tried to implement @Keenle's answer for define list objects inside a board: 基于在Swift中定义CoreData关系和这个 ,我尝试实现@Kenlele对板内定义列表对象的答案:
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)
}
}
However, I ran into the following error at board.lists.addListObject(lists)
: 'NSSet' does not have a member named 'addListObject'` 但是,我在
board.lists.addListObject(lists)
遇到以下错误: 'NSSet'没有名为'addListObject'的成员
Instead of board.lists.addListObject(lists)
, I also tried board.lists.listName = listName
as implied in this Obj-C example , but that sadly didn't work either. 而不是
board.lists.addListObject(lists)
,我也尝试了在这个Obj-C示例中隐含的board.lists.listName = listName
,但遗憾的是,这也没有用。
(Also, The println
output is correctly specifying the right board and list.) (另外,
println
输出正确指定了正确的板和列表。)
Thanks in advance! 提前致谢!
In a one-to-many relationship, it is easier to set the "to-one" direction of the inverse relationships, in your case just 在一对多关系中,在您的情况下,更容易设置反向关系的“一对一”方向
list.board = board
so that the extension methods are actually not needed here. 所以这里实际上不需要扩展方法。
You should invoke addListObject(...)
on board
object: 你应该在
board
对象上调用addListObject(...)
:
board.addListObject(list) // notice that we pass just one object
Additionaly, if you want to be able to add a set of lists to particular board
object, you can enhance you Board
class extension with methods that accept set of objects: 另外,如果您希望能够将一组列表添加到特定的
board
对象,则可以使用接受一组对象的方法来增强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)
}
}
If you define: 如果你定义:
@NSManaged var lists: Set<List>
Then you can do: 然后你可以这样做:
board.lists.insert(list)
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