ios4 - NSFetchedResultsController 错误 : The fetched object at index X has an out of order section name Y. 对象必须按部分名称排序'

Question

我正在 iphone 应用程序中实现搜索栏。我有 worker 列表，每个都有属性:名字、姓氏、公司。表 View 的部分设置为公司属性。

我在搜索时确实设置了谓词:

NSPredicate *predicate =[NSPredicate predicateWithFormat:@"firstName contains[cd] %@", searchBar.text];

我得到错误:

NSFetchedResultsController ERROR: The fetched object at index 3 has an out of order section name 'company2. Objects must be sorted by section name'

当我有 sortDescriptor 时:

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"lastName" ascending:YES selector:@selector(caseInsensitiveCompare:)]; 

我确实注意到当我将其更改为

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"firstName"` ascending:YES selector:@selector(caseInsensitiveCompare:)];

现在搜索工作正常，没有错误。 initWithKey 参数是否必须与谓词中的属性名称匹配？我不明白。

Answer 1

来自 NSFetchedResultsController 文档:

The fetch request must have at least one sort descriptor. If the controller generates sections, the first sort descriptor in the array is used to group the objects into sections; its key must either be the same as sectionNameKeyPath or the relative ordering using its key must match that using sectionNameKeyPath.

在您的情况下，您需要使用两种排序(在数组中)。第一个元素应该是公司名称属性的排序，第二个元素应该是 lastName/firstName 属性的排序。