由带有 CONTAINS 的谓词引起的异常答案

【问题标题】：Exception Caused by Predicate with CONTAINS由带有 CONTAINS 的谓词引起的异常
【发布时间】：2011-11-19 17:17:10
【问题描述】：

我遇到了这个奇怪的异常，我不知道如何找出这里出了什么问题

"Serious application error.  **Exception was caught during Core Data change processing.**  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  **Can't look for value (552284302) in string (1070635162, 630076961, 690758344, 714304224, 693603903, 650263092, 552284302); value is not a string  with userInfo (null)**"

我的代码如下：

- (NSFetchedResultsController *)fetchedResultsController {

if (_fetchedResultsController != nil) {
    return _fetchedResultsController;
}

NSManagedObjectContext *context =   [ (MyAppDelegate*)[[UIApplication sharedApplication] delegate]managedObjectContext];

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription 
                               entityForName:@"MyEntityName" inManagedObjectContext:context];
[fetchRequest setEntity:entity];

NSSortDescriptor *sort = [[NSSortDescriptor alloc] 
                          initWithKey:@"distance" ascending:YES];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];

[fetchRequest setFetchBatchSize:20];

User *user = [[DatabaseHelper sharedInstance] getUserDetails];
NSString *predicteString = [NSString stringWithFormat:@"isPrivate == %@  AND recepientList contains %@", [NSNumber numberWithBool:YES], user.userId];

if(dootType == UnReadDootType){
    predicteString = [predicteString stringByAppendingString:@" AND state = 'NEW' "];
}


NSPredicate *predicate;
if(senderId != nil && [senderId intValue] > 0){
    predicteString = [predicteString stringByAppendingString:@" AND senderId == %@"];

    predicate = [NSPredicate
                 predicateWithFormat:predicteString, senderId];

}else{
    predicate = [NSPredicate
                 predicateWithFormat:predicteString];
}

[fetchRequest setPredicate:predicate];


NSFetchedResultsController *theFetchedResultsController = 
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                    managedObjectContext:context sectionNameKeyPath:nil 
                                               cacheName:@"MyEntityName"];

self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;

[sort release];
[fetchRequest release];
[theFetchedResultsController release];

return _fetchedResultsController;    

}

NSFetchRequest 记录为：

<NSFetchRequest: 0x362350> (entity: MyEntityName; predicate: (isPrivate == 1 AND recepientList CONTAINS 552284302); sortDescriptors: ((
    "(distance, ascending, compare:)"
)); batch size: 20; type: NSManagedObjectResultType; )

如您所见，我使用了recepientList CONTAINS 552284302 之类的谓词对于我的记录之一，recepientList 有 1070635162, 630076961, 690758344, 714304224, 693603903, 650263092, 552284302 我将逗号分隔的 userId 存储在 recepientList 中，所以我不确定为什么会出现这个异常。

【问题讨论】：

标签： ios exception core-data

【解决方案1】：

user.userID 被解析为数值而不是字符串。 CONTAINS 运算符不理解数值。

记录为的谓词：

(isPrivate == 1 AND recepientList CONTAINS 552284302)

... 应该记录为：

(isPrivate == 1 AND recepientList CONTAINS "552284302")

前一个谓词寻找一个数值，而后一个谓词寻找一个字符串。（注意isPrivate == 1中的数字没有被引用。）

如果user.userID 是一个 NSNumber，那么获取它的字符串值应该可以解决问题。试试：

NSString *predicteString = [NSString stringWithFormat:@"isPrivate == %@  AND recepientList contains %@", [NSNumber numberWithBool:YES], [user.userId stringValue]];

【讨论】：

感谢 TechZen 的快速响应，user.userId 是 NSString，只是它不是 NSNumber，而且我每次都不会收到此错误，有时我会看到此错误，有时我不会.
好吧，我可以告诉你，记录的谓词将其视为一个数字。字符串应该是双引号或单引号。您可以使用带有recpientList 键的字典数组来测试谓词。您将收到与上述相同的错误。这显然是谓词解析的问题。

【解决方案2】：

感谢@TechZen，他的回答给了我一个提示，让我找出正确的答案。

@TechZen 你绝对正确，谓词应该记录为

(isPrivate == 1 AND recepientList CONTAINS "552284302")

但问题是 user.userId 不是 NSNumber 它是 NSString，所以问题出在这一行

NSString *predicteString = [NSString stringWithFormat:@"isPrivate == %@  AND recepientList contains %@", [NSNumber numberWithBool:YES], user.userId];

我把它改成了

 NSString *predicteString = [NSString stringWithFormat:@"isPrivate == %@ ", [NSNumber numberWithBool:YES]];

 predicteString = [predicteString stringByAppendingString:@"AND recepientList contains %@"];
 predicate = [NSPredicate
                 predicateWithFormat:predicteString, user.fbUserId];

就是这样，我按预期得到了它。我不知道为什么 NSString stringWithFormat 将 NSString 视为 NSNumber，而 NSPredicate 以正确的方式对待它。

【讨论】：