swift coredata 致命错误：在展开可选值时意外发现 nil

Question

for result in groups{
        let tmp = result.subject
        print("groups subject is \(tmp)")
}

我收到groups subject is MyGroupsData

我想在tableView cellForRowAtIndex中使用

        var channel : myEntity?
        groupsData = groups[indexPath.row] as? myEntity
        dataSubject = groupsData!.subject
        print("groups subject is \(dataSubject)")

显示groups subject is nil

原因：fatal error: unexpectedly found nil while unwrapping an Optional value

如何解决？

Answer 1

尝试使用

if let subject = groupsData?.subject {
dataSubject = subject
}

问题是 groupsData 为 nil，而您试图获取一个不存在的值。