Question

我遇到的问题是，只有我的字符串数组的最后一项保存在所需的核心数据实体中。

我有一个名为＆＃34; itemNames＆＃34;的多维数组。我将这个数组平面映射到一个简单的一维数组来迭代它。循环为每个项目创建一个保存在核心数据实体中的newItem＆＃34; CALC_VALUES＆＃34;在属性＆＃34; calc_item＆＃34;。

newItem的控制台输出看起来像预期的那样。

但是，当我加载实体＆＃34; CALC_VALUES＆＃34;的核心数据条目时，我会收到控制台输出2.它向我显示只有最后一项，＆＃34; item9＆＃34;保存在相应的实体中（参见控制台输出2）。

在迭代通过我的数组时，我需要更改代码以保存所有项目吗？

代码（swift 3）：

        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        var calc_values = [CALC_VALUES]()
        let itemNames = [["item1", "item2", "item3", "item4", "item5"], ["item6", "item7", "item8", "item9"]]

//----------- save items -----------//          

        // flat multidimensional array to array
        let flatItemNames = itemNames.flatMap({ $0 })

        // save each item from flatItemNames to core data entity "CALC_VALUES" in attribute "calc_item":
            for itemName in flatItemNames {
                var newItem = NSEntityDescription.insertNewObject (forEntityName: "CALC_VALUES", into: context) as NSManagedObject
                newItem.setValue(itemName, forKey: "calc_item")
                (UIApplication.shared.delegate as! AppDelegate).saveContext()

                // Checkpoint 1:  Check newItem values
                print ("***This is newItem: *** \(newItem)")              
            }


//----------- load items -----------//  

        // Checkpoint 2: Check core data entry
        let fetchRequest: NSFetchRequest<CALC_VALUES> = CALC_VALUES.fetchRequest()
        do {
            if let results = try context.fetch(fetchRequest) as? [CALC_VALUES] {
                calc_values = results as! [CALC_VALUES]
            }
        } catch {print ("no results")}
        print ("***This is calc_values: *** \(calc_values)")

控制台输出检查点1：

***This is newItem: *** <StartUpKit.CALC_VALUES: 0x6080000ad4a0> (entity: CALC_VALUES; id: 0x608000232a00 <x-coredata:///CALC_VALUES/t02F40B3E-95D3-4692-B630-2AEF16129A5F3> ; data: {
    "calc_item" = "item1";
    "calc_value" = 0;
})
***This is newItem: *** <StartUpKit.CALC_VALUES: 0x6000000ac1e0> (entity: CALC_VALUES; id: 0x600000235320 <x-coredata:///CALC_VALUES/t02F40B3E-95D3-4692-B630-2AEF16129A5F4> ; data: {
    "calc_item" = "item2";
    "calc_value" = 0;
})
***This is newItem: *** <StartUpKit.CALC_VALUES: 0x6000000ab880> (entity: CALC_VALUES; id: 0x600000236c80 <x-coredata:///CALC_VALUES/t02F40B3E-95D3-4692-B630-2AEF16129A5F5> ; data: {
    "calc_item" = "item3";
    "calc_value" = 0;
})

...

控制台输出检查点2：

***This is calc_values: *** [<StartUpKit.CALC_VALUES: 0x6000000aac20> (entity: CALC_VALUES; id: 0xd000000001f00000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p124> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aabc0> (entity: CALC_VALUES; id: 0xd000000001f40000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p125> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aab60> (entity: CALC_VALUES; id: 0xd000000001f80000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p126> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aab00> (entity: CALC_VALUES; id: 0xd000000001fc0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p127> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aaaa0> (entity: CALC_VALUES; id: 0xd000000002000000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p128> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aaa40> (entity: CALC_VALUES; id: 0xd000000002040000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p129> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aa9e0> (entity: CALC_VALUES; id: 0xd000000002080000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p130> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aa980> (entity: CALC_VALUES; id: 0xd0000000020c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p131> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aa680> (entity: CALC_VALUES; id: 0xd000000002100000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p132> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000aa5c0> (entity: CALC_VALUES; id: 0xd000000002140000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p133> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9ea0> (entity: CALC_VALUES; id: 0xd000000002180000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p134> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9d80> (entity: CALC_VALUES; id: 0xd0000000021c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p135> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9de0> (entity: CALC_VALUES; id: 0xd000000002200000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p136> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9cc0> (entity: CALC_VALUES; id: 0xd000000002240000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p137> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a99c0> (entity: CALC_VALUES; id: 0xd000000002280000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p138> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9900> (entity: CALC_VALUES; id: 0xd0000000022c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p139> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9240> (entity: CALC_VALUES; id: 0xd000000002300000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p140> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9120> (entity: CALC_VALUES; id: 0xd000000002340000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p141> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9180> (entity: CALC_VALUES; id: 0xd000000002380000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p142> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a9060> (entity: CALC_VALUES; id: 0xd0000000023c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p143> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a8d60> (entity: CALC_VALUES; id: 0xd000000002400000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p144> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a8ca0> (entity: CALC_VALUES; id: 0xd000000002440000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p145> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a6240> (entity: CALC_VALUES; id: 0xd000000002480000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p146> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a84c0> (entity: CALC_VALUES; id: 0xd0000000024c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p147> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000ac3c0> (entity: CALC_VALUES; id: 0xd000000002500000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p148> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000ac420> (entity: CALC_VALUES; id: 0xd000000002540000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p149> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000a8040> (entity: CALC_VALUES; id: 0xd000000002580000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p150> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000ac480> (entity: CALC_VALUES; id: 0xd0000000025c0000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p151> ; data: <fault>), <StartUpKit.CALC_VALUES: 0x6000000ab040> (entity: CALC_VALUES; id: 0xd000000002600000 <x-coredata://7687B389-1346-4C27-9B93-99B324FC28D2/CALC_VALUES/p152> ; data: {
    "calc_item" = "item9";
    "calc_value" = 0;
})]

Answer 1

快速浏览一下，您似乎使用相同的键“calc_item”保存每个项目。因此，每个保存都会覆盖前一个保存。

Answer 2

您必须将(UIApplication.shared.delegate as! AppDelegate).saveContext()置于for循环之外。

下面是完整的代码。

    let itemNames = [["item1", "item2", "item3", "item4", "item5"], ["item6", "item7", "item8", "item9"]]
    let flatItemNames = itemNames.flatMap({ $0 })

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    for itemName in flatItemNames {
        let managedContext = NSEntityDescription.insertNewObject(forEntityName: "CALC_VALUES", into: context)
        managedContext.setValue(itemName, forKey: "calc_item")
    }
    do {
        try context.save()
    } catch let error as NSError  {
        print("Error While Saving Data: \(error.userInfo)")
    }

要查看您的数据库通道，您可以使用SQLite Manager

下面是截图。

数组项未在核心数据实体中正确保存

2 个答案: