写入自动增量 ID答案

【问题标题】：Write auto increment id写入自动增量 ID
【发布时间】：2016-04-15 22:20:58
【问题描述】：

我正在使用 Swift 开发一个 iOs 程序，我正在使用 Core Data，我试图找到如何拥有一个自动增量 ID，我发现了这个：

但是这里没有问题，所以我试着看看如何编写一个自增属性：我在 .xcdatamodeld 文件中添加了一个名为“id”的新属性，我在 Objective-C 中找到了解决方案：

https://stackoverflow.com/a/22503259/5315947

但我不知道如何将其解析为 Swift2

我的代码：

    let appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let context: NSManagedObjectContext = appDel.managedObjectContext

    let newDemande = NSEntityDescription.insertNewObjectForEntityForName("Demandes", inManagedObjectContext: context)
    newDemande.setValue(soapRequest.xmlString, forKey: "xml")
    newDemande.setValue(1, forKey: "statutenvoie")

    do {
        try context.save()
    } catch {
        print("erreur data")
    }

    do {
        let request = NSFetchRequest(entityName: "Demandes")
        let results = try context.executeFetchRequest(request)

        if results.count > 0 {
            for item in results as! [NSManagedObject]{
                let xml = item.valueForKey("xml")
                let statutenvoie = item.valueForKey("statutenvoie")

                print(item.objectID)
                print(xml!, statutenvoie!)
            }
        }

    } catch {
        print("erreur data")
    }

UUID 错误：

代码：

let appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let context: NSManagedObjectContext = appDel.managedObjectContext

let newDemande = NSEntityDescription.insertNewObjectForEntityForName("Demandes", inManagedObjectContext: context)
newDemande.setValue(NSUUID().UUIDString, forKey: "id")
newDemande.setValue(soapRequest.xmlString, forKey: "xml")
newDemande.setValue(1, forKey: "statutenvoie")

do {
    try context.save()
} catch {
    print("erreur data")
}

do {
    let request = NSFetchRequest(entityName: "Demandes")
    let results = try context.executeFetchRequest(request)

    if results.count > 0 {
        for item in results as! [NSManagedObject]{

            let id = item.valueForKey("id")
            let xml = item.valueForKey("xml")
            let statutenvoie = item.valueForKey("statutenvoie")

            //                    print(item.objectID)
            print(id!, xml!, statutenvoie!)
        }
    }

} catch {
    print("erreur data")
}

错误：

2016-01-11 16:33:18.921 ...[2694:108875] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unacceptable type of value for attribute: property = "id"; desired type = NSNumber; given type = __NSCFString; value = 781EFF10-A9F1-4710-98C1-6D342B2EB480.'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000110a2be65 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x00000001132f8deb objc_exception_throw + 48
    2   CoreData                            0x00000001105c77b0 _PFManagedObject_coerceValueForKeyWithDescription + 2864
    3   CoreData                            0x000000011059f621 _sharedIMPL_setvfk_core + 177
    4   ...                             0x000000010ff690e5 _TFC7...29DemandeGratuiteViewController7ValiderfS0_FPSs9AnyObject_T_ + 4757
    5   ...                             0x000000010ff6aaa6 _TToFC7...29DemandeGratuiteViewController7ValiderfS0_FPSs9AnyObject_T_ + 54
    6   UIKit                               0x0000000112285e73 _UIGestureRecognizerSendTargetActions + 153
    7   UIKit                               0x00000001122824e5 _UIGestureRecognizerSendActions + 162
    8   UIKit                               0x00000001122804e2 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 843
    9   UIKit                               0x00000001122889a0 ___UIGestureRecognizerUpdate_block_invoke904 + 79
    10  UIKit                               0x000000011228883e _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 342
    11  UIKit                               0x0000000112276101 _UIGestureRecognizerUpdate + 2634
    12  UIKit                               0x0000000111e0df8a -[UIWindow _sendGesturesForEvent:] + 1137
    13  UIKit                               0x0000000111e0f1c0 -[UIWindow sendEvent:] + 849
    14  UIKit                               0x0000000111dbdb66 -[UIApplication sendEvent:] + 263
    15  UIKit                               0x0000000111d97d97 _UIApplicationHandleEventQueue + 6844
    16  CoreFoundation                      0x0000000110957a31 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    17  CoreFoundation                      0x000000011094d95c __CFRunLoopDoSources0 + 556
    18  CoreFoundation                      0x000000011094ce13 __CFRunLoopRun + 867
    19  CoreFoundation                      0x000000011094c828 CFRunLoopRunSpecific + 488
    20  GraphicsServices                    0x0000000114c2dad2 GSEventRunModal + 161
    21  UIKit                               0x0000000111d9d610 UIApplicationMain + 171
    22  ...                             0x000000010ff352cd main + 109
    23  libdyld.dylib                       0x0000000113e0a92d start + 1
    24  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

错误：

2016-01-12 09:13:03.726 ...[576:7439] CoreData: error: -addPersistentStoreWithType:SQLite configuration:(null) URL:file:///Users/informatiqueresponis/Library/Developer/CoreSimulator/Devices/314EFA4E-CC21-45A0-B3FD-FA486D52BB99/data/Containers/Data/Application/B0AB216F-D9B4-408D-ADB5-92BE2D333F62/Documents/SingleViewCoreData.sqlite options:(null) ... returned error Error Domain=NSCocoaErrorDomain Code=134100 "(null)" UserInfo={metadata={
    NSPersistenceFrameworkVersion = 641;
    NSStoreModelVersionHashes =     {
        Demandes = <e6fa8ed7 47097048 95c90274 cbc26ea7 decd6ea3 12e0df98 cd0d3cec da84d5ff>;
    };
    NSStoreModelVersionHashesVersion = 3;
    NSStoreModelVersionIdentifiers =     (
        ""
    );
    NSStoreType = SQLite;
    NSStoreUUID = "7C53DEAF-C47E-446B-913E-060946C728B0";
    "_NSAutoVacuumLevel" = 2;
}, reason=The model used to open the store is incompatible with the one used to create the store} with userInfo dictionary {
    metadata =     {
        NSPersistenceFrameworkVersion = 641;
        NSStoreModelVersionHashes =         {
            Demandes = <e6fa8ed7 47097048 95c90274 cbc26ea7 decd6ea3 12e0df98 cd0d3cec da84d5ff>;
        };
        NSStoreModelVersionHashesVersion = 3;
        NSStoreModelVersionIdentifiers =         (
            ""
        );
        NSStoreType = SQLite;
        NSStoreUUID = "7C53DEAF-C47E-446B-913E-060946C728B0";
        "_NSAutoVacuumLevel" = 2;
    };
    reason = "The model used to open the store is incompatible with the one used to create the store";
}
2016-01-12 09:13:03.730 ...[576:7439] Unresolved error Error Domain=YOUR_ERROR_DOMAIN Code=9999 "Failed to initialize the application's saved data" UserInfo={NSLocalizedDescription=Failed to initialize the application's saved data, NSLocalizedFailureReason=There was an error creating or loading the application's saved data., NSUnderlyingError=0x7fded60cdae0 {Error Domain=NSCocoaErrorDomain Code=134100 "(null)" UserInfo={metadata={
    NSPersistenceFrameworkVersion = 641;
    NSStoreModelVersionHashes =     {
        Demandes = <e6fa8ed7 47097048 95c90274 cbc26ea7 decd6ea3 12e0df98 cd0d3cec da84d5ff>;
    };
    NSStoreModelVersionHashesVersion = 3;
    NSStoreModelVersionIdentifiers =     (
        ""
    );
    NSStoreType = SQLite;
    NSStoreUUID = "7C53DEAF-C47E-446B-913E-060946C728B0";
    "_NSAutoVacuumLevel" = 2;
}, reason=The model used to open the store is incompatible with the one used to create the store}}}, [NSLocalizedDescription: Failed to initialize the application's saved data, NSLocalizedFailureReason: There was an error creating or loading the application's saved data., NSUnderlyingError: Error Domain=NSCocoaErrorDomain Code=134100 "(null)" UserInfo={metadata={
    NSPersistenceFrameworkVersion = 641;
    NSStoreModelVersionHashes =     {
        Demandes = <e6fa8ed7 47097048 95c90274 cbc26ea7 decd6ea3 12e0df98 cd0d3cec da84d5ff>;
    };
    NSStoreModelVersionHashesVersion = 3;
    NSStoreModelVersionIdentifiers =     (
        ""
    );
    NSStoreType = SQLite;
    NSStoreUUID = "7C53DEAF-C47E-446B-913E-060946C728B0";
    "_NSAutoVacuumLevel" = 2;
}, reason=The model used to open the store is incompatible with the one used to create the store}]
(lldb)

【问题讨论】：

可以使用UUID创建id
var uuid = NSUUID().UUIDString -> 76A4073A-D79C-45FD-A5D6-86E52AD8C771
@khuong291 怎么实现？
每次调用这个 var uuid = NSUUID().UUIDString。它将为您创建一个唯一的 ID
@khuong291 在核心数据中我创建了一个id属性Integer，那怎么办？我不是很明白 uuid = NSUUID().UUIDString，不是我看到的自动增量，而是如何将数据发送到属性？

标签： ios swift core-data

【解决方案1】：

仍然对您在评论中给出的示例感到困惑。我的回答是基于我理解您需要一个自动增加字段 - id，下次您插入新条目时。

如果您有两个字段，即xmlString 和id。然后首先你每次都使用SortDescriptor 和setFetchLimit = 1 进行获取请求。如果结果为空，则插入一个带有id = 1 的新条目。否则，使用id = oldId + 1 插入一个新条目。

我故意不提供任何代码，因为我不确定你真正想要什么。

顺便说一句，你最好使用自定义模型，即XCode生成的NSManagedObject，而不是当前的newDemande.setValue(value, forKey: "key")

编辑

提供的示例代码：

// Initialize Fetch Request
let fetchRequest = NSFetchRequest(entityName: "Demandes")

// Sort Descriptor
var idDescriptor: NSSortDescriptor = NSSortDescriptor(key: "id", ascending: false)
fetchRequest.sortDescriptors = [idDescriptor] // Note this is a array, you can put multiple sort conditions if you want

// Set limit
fetchRequest.fetchLimit = 1

var newId = 0; // Default to 0, so that you can check if do catch block went wrong later

do {
    let results = try self.managedObjectContext.executeFetchRequest(fetchRequest)

    //Compute the id
    if(results.count == 1) newId = results[0].id + 1 // slightly odd notation here, .id can be used if you use custom model. or you can use .valueForKey("id")
    else newId = 1 

} catch {
    let fetchError = error as NSError
    print(fetchError)
}

// Do the new insert afterwards

【讨论】：

这是一件好事 id = oldId + 1，但我如何将第一个条目设置为 1？
如果您的提取结果为空，则它是第一个条目。类似if(fetchedObjects.count == 1) { id = fetchedObjects[0].id + 1 } else { id = 1 }
好吧，你的意思是我自己写一个自增id，我去试试
但是我不太明白这些：SortDescriptor 和 setFetchLimit，你有例子吗？
这也是您想要定制模型的原因。

【解决方案2】：

我认为您正在发送一个字符串值 (781EFF10-A9F1-4710-98C1-6D342B2EB480) 并且核心数据需要一个 NSNumber (Int)。显然，781EFF10-A9F1-4710-98C1-6D342B2EB480 不是数字。

核心数据总是将 Int（Doubles、Float 等）值存储为 NSNumber，例如：

let intValue
let intValueInNSNumber = NSNumber(int: intValue)

区别在于intValue(Int)是原始类型，而NSNumber是对象。

属性“id”的类型是什么？

因为，如果属性是“Int”类型，则必须将其更改为“String”，它应该可以工作。

【讨论】：