Objective c 从核心数据获取数组
我已经用几个字符串字段和几个数组字段建立了一个模型。模型将保存为:Objective c 从核心数据获取数组,objective-c,ios,core-data,Objective C,Ios,Core Data,我已经用几个字符串字段和几个数组字段建立了一个模型。模型将保存为: - (void)saveLevel:(NSString*)level traps:(NSArray*)traps whirls:(NSArray*)whirls accels:(NSArray*)accels walls:(NSArray*)walls dest:(NSString*)dest jupiter:(NSString*)jupiter rating:(NSNumber*)pRating; { if (m
- (void)saveLevel:(NSString*)level traps:(NSArray*)traps whirls:(NSArray*)whirls accels:(NSArray*)accels walls:(NSArray*)walls dest:(NSString*)dest jupiter:(NSString*)jupiter rating:(NSNumber*)pRating;
{
if (m_pMOC == nil)
// Retrieves the managed object context
NSManagedObject* pNewLevel = [NSEntityDescription insertNewObjectForEntityForName:@"Level" inManagedObjectContext:m_pMOC];
NSDate* pDate = [NSDate date];
// Must have these four attributes
[pNewLevel setValue:level forKey:@"Level_ID"];
[pNewLevel setValue:jupiter forKey:@"Ball"];
[pNewLevel setValue:pDate forKey:@"Creation_Date"];
[pNewLevel setValue:dest forKey:@"Destination"];
[pNewLevel setValue:pRating forKey:@"Rating"];
// Optional attributes
if ([traps count] != 0)
[pNewLevel setValue:traps forKey:@"Traps"];
if ([whirls count] != 0)
[pNewLevel setValue:whirls forKey:@"Whirls"];
if ([accels count] != 0)
[pNewLevel setValue:accels forKey:@"Accelerators"];
if ([walls count] != 0)
[pNewLevel setValue:walls forKey:@"Walls"];
NSError* pError;
if (![m_pMOC save: &pError])
// etc...
}
- (void)saveLevel:(NSString*)level traps:(NSArray*)traps whirls:(NSArray*)whirls accels:(NSArray*)accels walls:(NSArray*)walls dest:(NSString*)dest jupiter:(NSString*)jupiter rating:(NSNumber*)pRating;
{
if (m_pMOC == nil)
{ // Code to get the managed object context from the delegate
}
NSManagedObject* pNewLevel = [NSEntityDescription insertNewObjectForEntityForName:@"Level" inManagedObjectContext:m_pMOC];
NSManagedObject* pNewBall = [NSEntityDescription insertNewObjectForEntityForName:@"Ball" inManagedObjectContext:m_pMOC];
[pNewBall setValue:jupiter forKey:@"a_Bounds"];
NSManagedObject* pNewDest = [NSEntityDescription insertNewObjectForEntityForName:@"Dest" inManagedObjectContext:m_pMOC];
[pNewDest setValue:dest forKey:@"a_Bounds"];
NSDate* pDate = [NSDate date];
// Must have these four attributes
[pNewLevel setValue:level forKey:@"a_Level_ID"];
[pNewLevel setValue:pDate forKey:@"a_Creation_Date"];
[pNewLevel setValue:pRating forKey:@"a_Rating"];
[pNewLevel setValue:@"Bob Dole" forKey:@"a_CreatedBy"];
[pNewLevel setValue:pNewBall forKey:@"r_Ball"];
[pNewLevel setValue:pNewDest forKey:@"r_Dest"];
// Optional attributes
if ([traps count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Trap"] addObjectsFromArray: traps];
if ([whirls count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Whirl"] addObjectsFromArray: whirls];
if ([accels count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Accel"] addObjectsFromArray: accels];
if ([walls count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Wall"] addObjectsFromArray: walls];
NSError* pError;
if (![m_pMOC save: &pError])
{ // Error saving
}
else
{ // Successfully saved
}
}
我有一个DataManager类,它处理从/到核心数据的获取/保存,在管理器内部,我验证了当我获取一个实体时,数组被获取,但是当它返回到调用它的类时,数组为零(另一方面,字符串刚好到达)。以下是提取代码和从提取中解析出返回值的代码:
- (NSArray*) getLevelWithID:(NSString*)level
{
NSEntityDescription *pEntityDescription = [NSEntityDescription entityForName:@"Level" inManagedObjectContext:m_pMOC];
NSFetchRequest *pRequest = [[[NSFetchRequest alloc] init] autorelease];
[pRequest setEntity:pEntityDescription];
NSPredicate* pPredicate = [NSPredicate predicateWithFormat:@"Level_ID == %@", level];
[pRequest setPredicate: pPredicate];
NSError* pError;
NSArray* pLevels = [m_pMOC executeFetchRequest:pRequest error:&pError];
if (pLevels == nil)
{
NSLog(@"Could not find the level with Level_ID = %@",level);
abort();
}
NSArray* pAccels = [pLevels valueForKey:@"Accelerators"];
NSArray* pTraps = [pLevels valueForKey:@"Traps"];
NSArray* pWalls = [pLevels valueForKey:@"Walls"];
NSArray* pWhirls = [pLevels valueForKey:@"Whirls"];
return pLevels;
}
我在最后四个数组上设置了一个断点,它们中有对象,但在检索它们的函数中(如下所示),它们是nil
- (void) initLevel:(NSArray*)pLevelObjects
{
Level* pLevel = [pLevelObjects objectAtIndex:0];
NSString* pJupiter = pLevel.Ball;
NSString* pDest = pLevel.Destination;
NSArray* pAccels = [pLevel valueForKey:@"Accelerators"];
NSArray* pTraps = [pLevel valueForKey:@"Traps"];
NSArray* pWalls = [pLevel valueForKey:@"Walls"];
NSArray* pWhirls = [pLevel valueForKey:@"Whirls"];
... (other initialization of the level) ...
}
我对此感到困惑。字符串值存在,但数组不存在。我最初尝试使用点符号(NSArray*pAccels=pLevel.Accelerators等),但结果相同
想法
编辑:从视图控制器调用initLevel:
- (void) startGameWithLevelID:(NSString*)pLevelID
{
NSLog(@"MyViewController - beginGameWithLevelID");
NSArray* pLevel = [[DataManager getDataManager] getLevelWithID:pLevelID];
if (pLevel == nil || [pLevel count] == 0)
{
NSLog(@"Didn't retrieve any level with id %@", pLevelID);
abort();
}
else
{
CGRect newFrame = makeScreen([UIScreen mainScreen].applicationFrame);
GameBoard* pGB = [[GameBoard alloc] initWithFrame: newFrame];
pGB.m_pMyVC = self;
[pGB initLevel: pLevel];
[self.view addSubview: (UIView*)pGB];
[pGB release];
}
}
编辑:我最近将数组重新分解成单独的实体,并与级别建立一对一的关系;该级别与这些实体具有多对多关系。我还更改了名称以更好地遵守约定:所有属性和关系现在都以小写字母开头。我分别用a_u和r_u作为属性和关系的前缀。保存“-[NSCFString\u iskindof entity:]:发送到实例0x4d83120的选择器无法识别时出错。这并没有太大的帮助,但我发现问题后会告诉你。目前,用于保存的代码如下所示:
- (void)saveLevel:(NSString*)level traps:(NSArray*)traps whirls:(NSArray*)whirls accels:(NSArray*)accels walls:(NSArray*)walls dest:(NSString*)dest jupiter:(NSString*)jupiter rating:(NSNumber*)pRating;
{
if (m_pMOC == nil)
// Retrieves the managed object context
NSManagedObject* pNewLevel = [NSEntityDescription insertNewObjectForEntityForName:@"Level" inManagedObjectContext:m_pMOC];
NSDate* pDate = [NSDate date];
// Must have these four attributes
[pNewLevel setValue:level forKey:@"Level_ID"];
[pNewLevel setValue:jupiter forKey:@"Ball"];
[pNewLevel setValue:pDate forKey:@"Creation_Date"];
[pNewLevel setValue:dest forKey:@"Destination"];
[pNewLevel setValue:pRating forKey:@"Rating"];
// Optional attributes
if ([traps count] != 0)
[pNewLevel setValue:traps forKey:@"Traps"];
if ([whirls count] != 0)
[pNewLevel setValue:whirls forKey:@"Whirls"];
if ([accels count] != 0)
[pNewLevel setValue:accels forKey:@"Accelerators"];
if ([walls count] != 0)
[pNewLevel setValue:walls forKey:@"Walls"];
NSError* pError;
if (![m_pMOC save: &pError])
// etc...
}
- (void)saveLevel:(NSString*)level traps:(NSArray*)traps whirls:(NSArray*)whirls accels:(NSArray*)accels walls:(NSArray*)walls dest:(NSString*)dest jupiter:(NSString*)jupiter rating:(NSNumber*)pRating;
{
if (m_pMOC == nil)
{ // Code to get the managed object context from the delegate
}
NSManagedObject* pNewLevel = [NSEntityDescription insertNewObjectForEntityForName:@"Level" inManagedObjectContext:m_pMOC];
NSManagedObject* pNewBall = [NSEntityDescription insertNewObjectForEntityForName:@"Ball" inManagedObjectContext:m_pMOC];
[pNewBall setValue:jupiter forKey:@"a_Bounds"];
NSManagedObject* pNewDest = [NSEntityDescription insertNewObjectForEntityForName:@"Dest" inManagedObjectContext:m_pMOC];
[pNewDest setValue:dest forKey:@"a_Bounds"];
NSDate* pDate = [NSDate date];
// Must have these four attributes
[pNewLevel setValue:level forKey:@"a_Level_ID"];
[pNewLevel setValue:pDate forKey:@"a_Creation_Date"];
[pNewLevel setValue:pRating forKey:@"a_Rating"];
[pNewLevel setValue:@"Bob Dole" forKey:@"a_CreatedBy"];
[pNewLevel setValue:pNewBall forKey:@"r_Ball"];
[pNewLevel setValue:pNewDest forKey:@"r_Dest"];
// Optional attributes
if ([traps count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Trap"] addObjectsFromArray: traps];
if ([whirls count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Whirl"] addObjectsFromArray: whirls];
if ([accels count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Accel"] addObjectsFromArray: accels];
if ([walls count] != 0)
[[pNewLevel mutableSetValueForKey: @"r_Wall"] addObjectsFromArray: walls];
NSError* pError;
if (![m_pMOC save: &pError])
{ // Error saving
}
else
{ // Successfully saved
}
}
再次感谢您的帮助,抱歉这篇文章太长,但我希望这能帮助其他核心数据新手(如我)学到一些东西
最终编辑:好的,在重构之后,我终于找到了将数组保存为对象的解决方案(尽管我不确定这是否是最有效的方法)。下面是添加一堆“陷阱”的代码。传递到函数中的数组是陷阱的边界,它将被存储。然后与级别形成关系(注意,不必同时由陷阱和级别设置,只需其中一个,因为核心数据以另一种方式处理)
可能的阵列误用
在第一个代码段中,您正在NSArray
上调用valueForKey:
,结果是一个数组,因为该代码迭代pLevels
,将valueForKey:
参数传递给内部的每个对象并组合值
这就是为什么
在第二段代码中,首先从数组中获取一个pLevel,然后对实体而不是数组执行valueForKey:
选择器。所以结果就是这个特定的物体里的东西
可能您的某些实体具有这些字段,因此所有这些字段的组合结果具有一些值,但某些特定的结果不具有这些值
可能的核心数据滥用
您说您在核心数据实体中保留了一个数组。你是怎么做到的?没有特殊类型来保存数组,因此通常必须将其存储为二进制数据,并使用[NSKeyedArchiver archivedDataWithRootObject:array]
执行编码。可能是存储和获取不正确,因为您试图在非数组字段中存储数组
您是否也遇到过任何崩溃?在视图控制器中,阵列仍有对象。。。可能需要保留。如果存在保留问题,您将在
级别*pLevel=[pLevelObjects objectAtIndex:0]
上崩溃。我将在下班(或有空闲时间)时研究第一种情况。至于第二种情况,我尝试将数据库中的对象声明为二进制数据(NSData),而不是“未定义”(和“瞬态”,这是我记得core data ref说要使用数组的方式),但这似乎并没有缓解问题。我正在考虑将数组重构成单独的实体,每个实体与级别之间都有“对一”的关系(级别与级别之间都有“对多”的关系)。唯一的问题是,文档中没有非常清楚地说明如何有效地批量保存这些新实体。我甚至想不出我会怎么做。你知道最好的方法吗?这一定是一个核心数据误用问题,因为使用点表示法(例如pLevel.Accelerators)会出现零数组,我会编辑帖子,包括save,看看我是否对NSManagedObject
子类做了错误的事情,使用valueForKey:
和点表示法是一样的,除非你超越了valueForKey:
你自己。它将调用相同的方法并返回相同的结果。