NSPredicate SUBQUERY导致：[NSMutableSet unionSet] set参数不是NSSet [英] NSPredicate SUBQUERY results in: [NSMutableSet unionSet] set argument is not an NSSet

问题描述

在一系列歌手中，我尝试使用以下格式执行 filteredArrayUsingPredicate ，以便仅留给拥有至少一个专辑且至少包含一首Intro歌曲的歌手。

On an array of Artists I am trying to do filteredArrayUsingPredicate using the below format to only remain with Artists that have at least one Album that has at least one Intro song.

相册是从歌手到专辑的多对多关系。 intros 是一个从专辑到简介的多对多关系。我得到一个异常，说 [NSMutableSet unionSet：]：set参数不是NSSet 。我究竟做错了什么？这是上述谓词格式：

albums is a to many relationship from Artist to Album. intros is a to many relationship from Album to Intro. I get an exception saying [NSMutableSet unionSet:]: set argument is not an NSSet. What am I doing wrong? Here is the aforementioned predicate format:

@"SUBQUERY(albums, $alb, ANY $alb.intros != NULL).@count != 0"

推荐答案

似乎/是苹果核心数据框架中的错误。我确认这一点是因为我不再遇到此问题。我根本没有解决。我试过了，这样可以减少例外发生的频率，但没有消除它。

It seems like there is/was a bug in apples Core-data framework. I confirm this because I do not encounter this issue anymore. I did not address it at all. I tried to, and that reduced the frequency of the exception, but did not extinguish it.

看看此链接以获取有关如何解决此类问题的建议。

Have a look at this link for suggestions on how to solve this sort of issue.

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