替换 CoreData 中的属性

Posted 2023-03-05

【中文标题】替换 CoreData 中的属性

【英文标题】：replacing attribute within CoreData

【发布时间】：2016-03-12 14:55:45

【问题描述】：

我在 CoreDate 中有一个名为 BudgetDetail 的实体。我有下面的代码，我想更新属性“剩余”，但它似乎是添加新记录而不是更新。

func checksBudgetDetail(budgetName: String, spendAmount: Double, date: NSDate)
        print("budget name = \(budgetName)")

        //fetch results fron income entity and place in array
        let budgetDetailResults: [AnyObject] = try! context.executeFetchRequest(budgetDetail)
     print("budget results loaded")

        //if there are no incomes saved, do nothing.
        if budgetDetailResults.isEmpty 
        

        //if there are incomes saved, retrieve name and amount
        else 
            for i in budgetDetailResults 
                print("in loop")

                 let name = (i.valueForKey(budgetNameKeyToUpdate)! as! String)
                let amount = Double(i.valueForKey(budgetAmountKeyToUpdate)!.stringValue)
                let durationType = (i.valueForKey(budgetDurationTypeKeyToUpdate)! as! String)
                let durationOccurance = Double(i.valueForKey(budgetDurationOccuranceKeyToUpdate)!.stringValue)
                let remaining = (i.valueForKey(budgetRemaningKeyToUpdate)!.stringValue)
                let startDate = (i.valueForKey(startDateKeyToUpdate)! as! NSDate)
                let endDate = (i.valueForKey(endDateKeyToUpdate)! as! NSDate)

                if name == budgetName 
                    print("just logged a spend against the budget \(name)")

                    //if the date in the on the spend is within the startDate and endDate, call the updateBudgetDetailEntity to update the remaining budget
                    if startDate.compare(date) == .OrderedAscending && endDate.compare(date) == .OrderedDescending 

                        print("the spend which has just been logged is also within the dates of \(name)'s budget")

                        let newRemaining : Double

                        print("\(budgetName) has a old reamining amount of:\(remaining)")

                        newRemaining = Double(remaining)! - spendAmount

                        print("\(budgetName) has a new reamining amount of:\(newRemaining)")

                        let entity = NSEntityDescription.entityForName("BudgetDetail", inManagedObjectContext: context)!
                        let saveBudgetEntity = NSManagedObject(entity: entity, insertIntoManagedObjectContext:context)

                        // add user input to the relevant entity
                        saveBudgetEntity.setValue(name, forKey: budgetNameKeyToUpdate)
                        saveBudgetEntity.setValue(amount, forKey: budgetAmountKeyToUpdate)
                        saveBudgetEntity.setValue(durationType, forKey: budgetDurationTypeKeyToUpdate)
                        saveBudgetEntity.setValue(durationOccurance, forKey: budgetDurationOccuranceKeyToUpdate)
                        saveBudgetEntity.setValue(startDate, forKey: startDateKeyToUpdate)
                        saveBudgetEntity.setValue(endDate, forKey: endDateKeyToUpdate)
                        saveBudgetEntity.setValue(newRemaining, forKey: budgetRemaningKeyToUpdate)


                    do 
                        try context.save()
                        print("new remaining attriute saved")
                     catch _ 
                        print("new remaining attriute didnt saved")
                    


                    
                    else 
                        //would need to create a new record with new start and end dates
                    
                
                else 

                

               print("\(date)")
                print("Name:\(budgetName), startDate:\(startDate), endDate:\(endDate)")
            
        

看起来好像添加了一条新记录，而不是在循环中更新一条记录。我不确定为什么会这样，任何帮助将不胜感激。

【参考方案1】：

这些行：

let entity = NSEntityDescription.entityForName("BudgetDetail", inManagedObjectContext: context)!
let saveBudgetEntity = NSManagedObject(entity: entity, insertIntoManagedObjectContext:context)
// add user input to the relevant entity
saveBudgetEntity.setValue(name, forKey: budgetNameKeyToUpdate)
saveBudgetEntity.setValue(amount, forKey: budgetAmountKeyToUpdate)
saveBudgetEntity.setValue(durationType, forKey: budgetDurationTypeKeyToUpdate)
saveBudgetEntity.setValue(durationOccurance, forKey: budgetDurationOccuranceKeyToUpdate)
saveBudgetEntity.setValue(startDate, forKey: startDateKeyToUpdate)
saveBudgetEntity.setValue(endDate, forKey: endDateKeyToUpdate)
saveBudgetEntity.setValue(newRemaining, forKey: budgetRemaningKeyToUpdate)

创建一个新的托管对象并设置其属性值。如果您只想更新现有对象，请删除这些行并替换为：

i.setValue(newRemaining, forKey: budgetRemaningKeyToUpdate)