英文:
how to set up a core data relationship between 2 classes with 2 different tableviews
问题
在我的Swift代码中，我有一个用于城市的类和一个用于州的类。州可以有多个城市，但一个城市只能属于一个州。我不确定是否正确设置了我的核心数据属性，特别是反向部分。我知道如何在属性面板上将其更改为一对多。我只是想知道是否漏掉了任何操作。当用户选择一个州时，它将跳转到一个新的类，在那里用户可以将城市保存到只属于该特定州的状态。
英文:
In my swift code I have one class for cities and one class for states. States can have many cities but a city can only have 1 state. I don't know if I set up my core data attributes correctly especially the inverse part. I know how to change it to one to many on the propties panel. I am just wondering if I am missing anything to do this. When the user selects a States it will go to a new class where the user can saves cities to only that specific state.
答案1
得分: 1
以下是翻译好的内容：
我在我的项目中已经做过这种类型的事情，但是虽然从我的角度来看，我没有清楚地理解你的问题，我可以说我在我的项目中所做的类似于以下内容：
State 实体: -
属性: -
stateN: 字符串
关系: -
city: 一对多关系（目标: 城市，反向: state）
City 实体: -
属性: -
cityN: 字符串
关系: -
state: 一对一关系（目标: State，反向: city）
现在，如果您想选择一个州并希望将一个城市保存到该特定州，请创建一个新的 City 实例，然后设置新城市的 cityN 属性。将新城市的 state 关系设置为所选的州。
let context = persistentContainer.viewContext
// 创建一个新的州
let state = State(context: context)
state.stateN = "Kerala"
// 创建一个新的城市
let city = City(context: context)
city.cityN = "Calicut"
// 将城市与州关联
city.state = state
// 保存更改
do {
try context.save()
} catch {
print("保存上下文时出错：\(error)")
}
请注意：上述代码是用 Swift 编写的，并假定您正在使用 Core Data 来管理数据。
英文:
I have done this type of things in my project, but I didn't understand your question clearly eventhough on my perspective I can say that like what I have done in my project
State entity:-
Attribute:-
stateN: String
Relationship:-
city: To-Many relationship (Destination: City, Inverse: state)
City entity:-
Attribute:-
cityN: String
Relationship:-
state: To-One relationship (Destination: State, Inverse: city)
and now if you want to selects a state and wants to save a city to that specific state.Create a new instance of City then Set the cityN attribute for new city.Set the state relationship of the new city to the selected state.
let context = persistentContainer.viewContext
// Create a new state
let state = State(context: context)
state.stateN = "Kerala"
// Create a new city
let city = City(context: context)
city.cityN = "Calicut"
// Associate the city with the state
city.state = state
// Save the changes
do {
try context.save()
} catch {
print("Error saving context: \(error)")
}
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