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我想你快到了。问题似乎不在于您如何打电话selectField或processOptions. 问题是该调用的结果将是一个Entity Process，而第二个字段Report是一个ProcessId。所以你只需要使用fmap(aka <$>) 来转换。我相信以下会做到这一点：
selectField
processOptions
Entity Process
Report
ProcessId
fmap
<$>
entityKey <$> (areq (selectField processOptions) "Process" Nothing)