如何保存领域关系(列表)
问题描述:
我曾尝试将领域对象保存到我的数据库,但它不起作用。如何保存领域关系(列表)
这里是我的模型:
class CreditCard: Object {
dynamic var owner: String?
var purchases: List<Purchase>()
}
,二类它看起来像:
class Purchase: Object {
dynamic var id: Int = 0
dynamic var name: String?
dynamic var data: String?
let creditCard = LinkingObjects(fromType: CreditCard.self, property: "purchases")
}
我可以保存所有的CreditCard对象就好了。
在另一个视图控制器上,我有另一个请求,要下载所有购买的信用卡。该请求后,这是我尝试写的境界:
let creditCard = realm.objects(CreditCard.self).first // there's some code to get this.
try! realm.write {
for purchase in purchases { // purchases = objects from a son
let newPurchase = Purchase()
newPurchase.id = purchase["Id"].intValue
newPurchase.name = purchase["name"].stringValue
newPurchase.date = purchase["date"].dateValue
creditCard.purchases.append(newPurchase)
realm.add(creditCard, update: true)
}
}
出于某种原因,所有的采购,当应用程序关闭对象都将丢失。购买被保存在我的领域对象上,但CreditCard和Purchase之间的关系丢失。所以,当我重新打开应用程序时,从下面的代码返回总是空的:
let purchases = creditCard.purchases
我在做什么错了?
答
您还需要保存购买,不仅在父信用卡对象中。
let creditCard = realm.objects(CreditCard.self).first // there's some code to get this.
try! realm.write {
for purchase in purchases { // purchases = objects from a son
let newPurchase = Purchase()
newPurchase.id = purchase["Id"].intValue
newPurchase.name = purchase["name"].stringValue
newPurchase.date = purchase["date"].dateValue
realm.add(newPurchase) // <-- save the purchase object to realm
creditCard.purchases.append(newPurchase)
}
}
信用卡对象已存在于领域,因此不要再添加它。
谢谢。它解决了其中一个问题。现在,每次我下载信用卡清单并在领域进行更新时,都会失去采购。 不应该realm.add(newCreditCard,update:true)保持所有购买关系(如果信用卡已经存在于领域)? – hdoria