在ios swift中核心数据分组无法正常工作
我是PHP Web开发人员。 我最近学到了ios。 我试图从核心数据中获取logging，并根据ios swift中的一个属性合适地根据一列或多列对logging进行分组。 我已经尝试了堆栈溢出的解决scheme，但他们都没有为我工作。 所以请有人指出我做错了什么。 这是我的代码：
var context : NSManagedObjectContext = appdel.managedObjectContext! var request = NSFetchRequest(entityName: "TblOrders") request.returnsObjectsAsFaults = false request.propertiesToGroupBy = ["order_num"] request.propertiesToFetch = ["cust_name", "brand"] request.resultType = .DictionaryResultType context.executeFetchRequest(request, error: nil)! var results = context.executeRequest(request, error: nil)! println(results) 这是错误信息：
2015-08-11 10:54:30.423 newapp[470:6013] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'SELECT clauses in queries with GROUP BY components can only contain properties named in the GROUP BY or aggregate functions ((<NSAttributeDescription: 0x7fa8ca5b4b70>), name cust_name, isOptional 1, isTransient 0, entity TblOrders, renamingIdentifier cust_name, validation predicates ( ), warnings ( ), versionHashModifier (null) userInfo { }, attributeType 700 , attributeValueClassName NSString, defaultValue (null) is not in the GROUP BY)' *** First throw call stack: ( 0 CoreFoundation 0x0000000101e35c65 __exceptionPreprocess + 165 1 libobjc.A.dylib 0x00000001039a0bb7 objc_exception_throw + 45 2 CoreData 0x0000000101a4fbbc -[NSSQLGenerator newSQLStatementForRequest:ignoreInheritance:countOnly:nestingLevel:] + 1724 3 CoreData 0x0000000101a3bdc4 -[NSSQLAdapter _statementForFetchRequest:ignoreInheritance:countOnly:nestingLevel:] + 244 4 CoreData 0x0000000101953e0c -[NSSQLAdapter _newSelectStatementWithFetchRequest:ignoreInheritance:] + 316 5 CoreData 0x0000000101953a86 -[NSSQLCore newRowsForFetchPlan:] + 118 6 CoreData 0x000000010195333c -[NSSQLCore objectsForFetchRequest:inContext:] + 524 7 CoreData 0x0000000101952dbb -[NSSQLCore executeRequest:withContext:error:] + 299 8 CoreData 0x0000000101a2da6c __65-[NSPersistentStoreCoordinator executeRequest:withContext:error:]_block_invoke + 3356 9 CoreData 0x0000000101a36c30 gutsOfBlockToNSPersistentStoreCoordinatorPerform + 192 10 libdispatch.dylib 0x00000001040a2614 _dispatch_client_callout + 8 11 libdispatch.dylib 0x0000000104088002 _dispatch_barrier_sync_f_invoke + 365 12 CoreData 0x0000000101a28245 _perform + 197 13 CoreData 0x0000000101952a58 -[NSPersistentStoreCoordinator executeRequest:withContext:error:] + 504 14 CoreData 0x00000001019512ca -[NSManagedObjectContext executeFetchRequest:error:] + 586 15 newapp 0x000000010165ea9a _TFC6newapp25OrderStatusViewController11viewDidLoadfS0_FT_T_ + 1418 16 newapp 0x000000010165efe2 _TToFC6newapp25OrderStatusViewController11viewDidLoadfS0_FT_T_ + 34 17 UIKit 0x00000001028051d0 -[UIViewController loadViewIfRequired] + 738 18 UIKit 0x00000001028053ce -[UIViewController view] + 27 19 UIKit 0x000000010282a257 -[UINavigationController _startCustomTransition:] + 633 20 UIKit 0x000000010283637f -[UINavigationController _startDeferredTransitionIfNeeded:] + 386 21 UIKit 0x0000000102836ece -[UINavigationController __viewWillLayoutSubviews] + 43 22 UIKit 0x00000001029816d5 -[UILayoutContainerView layoutSubviews] + 202 23 UIKit 0x00000001027549eb -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 536 24 QuartzCore 0x0000000106522ed2 -[CALayer layoutSublayers] + 146 25 QuartzCore 0x00000001065176e6 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380 26 QuartzCore 0x0000000106517556 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24 27 QuartzCore 0x000000010648386e _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 242 28 QuartzCore 0x0000000106484a22 _ZN2CA11Transaction6commitEv + 462 29 QuartzCore 0x00000001064850d3 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 89 30 CoreFoundation 0x0000000101d68ca7 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23 31 CoreFoundation 0x0000000101d68c00 __CFRunLoopDoObservers + 368 32 CoreFoundation 0x0000000101d5ea33 __CFRunLoopRun + 1123 33 CoreFoundation 0x0000000101d5e366 CFRunLoopRunSpecific + 470 34 GraphicsServices 0x0000000105e09a3e GSEventRunModal + 161 35 UIKit 0x00000001026d48c0 UIApplicationMain + 1282 36 newapp 0x0000000101678747 main + 135 37 libdyld.dylib 0x00000001040d6145 start + 1 38 ??? 0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException
我已经从这里尝试了解决scheme： Swift核心数据 – 组不起作用
如果有任何进一步的信息，请让我知道。
最后我可以解决这个问题。 虽然我没有目标C的知识，但我在目标C中search了相同的问题，并得到了解决Swift问题的想法。 它可以帮助那些可能面临同样问题的人，所以我在这里分享我的解决scheme。
问题是propertiesToGroupBy必须包含所有要由propertiesToFetch获取的元素。 为了清晰起见，我在这里分别粘贴这两行代码：
request.propertiesToGroupBy = ["order_num","cust_name"] request.propertiesToFetch = ["order_num","cust_name"]
观察上面的代码行都有元素（属性）order_num和cust_name。 （这只是我的代码中的一个例子，但我们可以添加尽可能多的元素）
以下是我的上述问题的完整代码解决scheme：
var context : NSManagedObjectContext = appdel.managedObjectContext! var request = NSFetchRequest(entityName: "TblOrders") request.returnsObjectsAsFaults = false request.propertiesToGroupBy = ["order_num","cust_name"] request.propertiesToFetch = ["order_num","cust_name"] request.resultType = .DictionaryResultType context.executeFetchRequest(request, error: nil)! var res = context.executeFetchRequest(request, error: nil)! var results = res as NSArray println(results)