Coredata toMany关系映射问题 - Swift

Posted 2023-03-05

【中文标题】Coredata toMany关系映射问题 - Swift

【英文标题】：Coredata toMany relationship mapping issue - Swift

【发布时间】：2015-03-11 11:57:21

【问题描述】：

我有两个表 Category 和 Sub Category。

Category 与 SubCategory 有 toMany 关系。 SubCategory 与 SubCategory 有 toMany 关系。 （SubCategory 可能有子类别）

数据库模型：

Json 响应

"response": 
    "status": true,
    "message": "Category listed",
    "code": 200
,
"data": [
    
        "description": "Memory Questions",
        "id": "QT05",
        "title": "Memory",
        "subcategory": [
            
                "title": "Patterns",
                "id": "QT05P",
                "subcategory": [
                    
                        "title": "Squares",
                        "id": "QT05PS",
                        "demo": 
                            "type": "image",
                            "value": "Memory/images/demo_QT05PS.png"
                        
                    ,
                    
                        "title": "Circles",
                        "id": "QT05PC",
                        "demo": 
                            "type": "image",
                            "value": "Memory/images/demo_QT05PC.png"
                        
                    ,
                    
                        "title": "Triangles",
                        "id": "QT05PT",
                        "demo": 
                            "type": "image",
                            "value": "Memory/images/demo_QT05PT.png"
                        
                    ,
                    
                        "title": "Rectangles",
                        "id": "QT05PR",
                        "demo": 
                            "type": "image",
                            "value": "Memory/images/demo_QT05PR.png"
                        
                    
                ],
                "demo": 
                    "type": "image",
                    "value": "Memory/images/demo_QT05P.png"
                
            
        ]
    
]

子类别模型类（CoreData）

extension SubCategory
    func addSubCategory(subcategory:SubCategory) 
        var sub = self.mutableSetValueForKey("subcategories")
        sub.addObject(subcategory)
    

    func setSubCategories(subCategories:NSArray)
        var sub = self.mutableSetValueForKey("subcategories")
        for subcategory in subCategories 
            sub.addObject(subcategory)
        
    

映射 JSON

func mapCategory(dict:NSDictionary?) -> LUBaseResponse? 
    if (dict == nil) 
        return nil
    
    var response = self.mapStatus(dict!)
    if (response != nil)
        if (response!.status == 1)
            let data:NSArray = dict!["data"] as NSArray
            var categoryArray = NSMutableArray()
            for categoryDict in data 
                if (self.fetchCategory(categoryDict["id"] as? String) == nil)
                    var category = NSEntityDescription.insertNewObjectForEntityForName("Category", inManagedObjectContext: self.managedObjectContext!) as? Category
                    category?.categoryDescription = categoryDict["description"] as String
                    category?.categoryId = categoryDict["id"] as String
                    category?.categoryTitle = categoryDict["title"] as String
                    var subcategory = self.mapSubcategory(categoryDict["subcategory"] as? NSArray,category: category!)
                    if (subcategory != nil && subcategory?.count > 0)
                        category?.setSubCategories(subcategory!)
                    
                    categoryArray.addObject(category!)
                
                LUCoreData.sharedInstance.saveContext()
            
            response?.data = categoryArray

        
    
    return response




//Issue in this method
     private func mapSubcategory(array:NSArray?,category:Category) -> NSMutableArray? 
            var subcategoriesObjects = NSMutableArray()
            if (array?.count > 0)
                var subcategories = array!
                NSEntityDescription.insertNewObjectForEntityForName("SubCategory", inManagedObjectContext: self.managedObjectContext!) as? SubCategory
                for subcategoryDict in subcategories 
                    var title = subcategoryDict["title"]

                    if (self.fetchSubCategory(subcategoryDict["id"] as? String) == nil) 
                        var subcategory = NSEntityDescription.insertNewObjectForEntityForName("SubCategory", inManagedObjectContext: self.managedObjectContext!) as? SubCategory
                        subcategory?.title = subcategoryDict["title"] as String
                        subcategory?.id    = subcategoryDict["id"] as String
                        subcategory?.categoryOf = category

                        var arraySubCategory = subcategoryDict.objectForKey("subcategory") as? NSArray
                        if (arraySubCategory?.count > 0)
                            var nestedSubCategory = self.mapSubcategory(arraySubCategory,category: category)
                            if (nestedSubCategory != nil)
                            var sub = nestedSubCategory!.objectAtIndex(0) as SubCategory
                                println("Sub is \(sub.subcategories)") //Returns Empty
                                subcategory!.setSubCategories(nestedSubCategory!)
                               //Issue Here
                             println("Sub is \(sub.subcategories)") 
                            
                        
                        subcategoriesObjects.addObject(subcategory!)
                    
                    LUCoreData.sharedInstance.saveContext()
                
            
            return subcategoriesObjects
        

问题：

在 JSON Response 中，您可以看到 Memory(Category) 有子类别“Patterns”，其中嵌套了 SubCategories “Square”、“Circles”等。

这个循环在“mapSubcategory”函数中执行

在这一行之后“subcategory!.setSubCategories(nestedSubCategory!)”

在上图中，您可以看到当嵌套子类别（“Squares”没有进一步的子类别）添加到父子类别时，父子类别（模式）作为子类别添加到 Square。这会导致递归（父 -> 子 -> 父 -> 子 ....）。我不确定它是如何递归地将父级添加到子级的。

【参考方案1】：

我已通过从子类别表中删除反向关系来解决此问题。