使用LInkingOjbects在Realm运行时发生致命错误

Question

获取以下致命错误。这里

fatal error: 'try!' expression unexpectedly raised an error: Error Domain=io.realm Code=1 "Schema validation failed due to the following errors: - Property 'GearModel.category' declared as origin of linking objects property 'CategoryRepository.gearList' links to type 'CategoryModel'" UserInfo={NSLocalizedDescription=Schema validation failed due to the following errors: - Property 'GearModel.category' declared as origin of linking objects property 'CategoryRepository.gearList' links to type 'CategoryModel', Error Code=1}:

对象模型：齿轮模型被分配给一个唯一的类别

import Foundation 
import RealmSwift 

class GearModel: Object{ 

    dynamic var gearID = NSUUID().uuidString 
    dynamic var name = "" 
    dynamic var manufacturer = "" 
    dynamic var sortOrder = 0 
    dynamic var category: CategoryModel? 

    override class func primaryKey() -> String? {return "gearID"} 
    } 

分类型号：试图获得与分配的类别所有GearModel的产品清单。

import Foundation 
    import RealmSwift 

    class CategoryModel: Object{ 

     dynamic var categoryID = NSUUID().uuidString 
     dynamic var sortOrder = 0 
     dynamic var name = "" 
     let gearList = LinkingObjects(fromType: GearModel.self, property: "category") 

override class func primaryKey() -> String? {return "categoryID"} 
    } 

类别库类：行发生致命错误 “让境界= ....”，在allCategories（）FUNC

import Foundation 
import RealmSwift 

class CategoryRepository: CategoryModel{ 

    class func GetGearItemsForCategory(CategoryID: String) -> Results<GearModel> 
    { 
     let realm = try! Realm() 

     var gearItems = realm.objects(GearModel.self) 

     let predicate = NSPredicate(format: "categoryID = %@", CategoryID) 
     gearItems = gearItems.filter(predicate) 
     return gearItems 
    } 

    class func GetCountOfGearItems(CategoryID: String) -> Int 
    { 
     let realm = try! Realm() 

     var gearItems = realm.objects(GearModel.self) 

     let predicate = NSPredicate(format: "categoryID = %@", CategoryID) 
     gearItems = gearItems.filter(predicate) 
     return gearItems.count 
    } 

    class func AddCategory(CategoryID: String, Name: String, SortOrder: Int){ 

     let realm = try! Realm() 

     let category = CategoryModel(name: CategoryID, categoryID: Name, sortOrder: SortOrder) 

     try! realm.write { 
      realm.add(category) 
     } 
    } 

    class func allCategories() -> Results<CategoryModel> { 

     let realm = try! Realm() 


     return realm.objects(CategoryModel.self).sorted(byProperty: "SortOrder") 
    } 

Answer 1

从具有LinkingObjects属性的类继承不被支持。

Realm中的对象和列表属性不是协变的，这意味着它们只能指向完全指定的类，而不指向该类的子类。这意味着GearModel.category无法链接到CategoryRepository对象，但CategoryRepository具有继承的gearList属性，该属性试图列出链接到该对象的对象GearModel。

在您的具体情况下，不清楚为什么CategoryRepository继承自CategoryModel。