CoreData：过滤FetchRequest结果为零

Question

我正在尝试过滤对CD的获取请求，并且最初它工作但现在它返回一个空数组。我检查了实体（Provider），我试图过滤的密钥名称是正确的（providerName）。我已经检查了SQLite数据库和记录，其名称与我正在搜索的providerName相匹配。 （见下面附图）。有人可以审查我的代码，看看我做错了吗？感谢：

- (NSArray* ) filterItemsFromCoreData : (NSArray* ) filters { 

//create a managed object context
NSManagedObjectContext* context = [self managedObjectContext];

//create error container and fetch request
NSError* errMsg;
NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init];

//get our filters from passed array
NSString* filterProviderName = [filters objectAtIndex:0];
NSString* filterProviderZip = [filters objectAtIndex:1];
NSString* filterProviderPhone = [filters objectAtIndex:2];

//create predicate
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"providerName == %@", filterProviderName];

//create entity description
NSEntityDescription *entity = [NSEntityDescription
                               entityForName:@"Provider" inManagedObjectContext:context];

//add entity and predicate to fetch request
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];

//get the objects
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&errMsg];
NSLog(@"%@", fetchedObjects);
return fetchedObjects;
}

实体屏幕捕获

SQLite DB

Answer 1

将谓词格式中的格式说明符%@更改为单引号'%@'。

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"providerName == '%@'", filterProviderName];

这应该会再次返回结果。