Question

我正在使用一个表视图控制器来根据用户的职业划分用户。我从字典开始，然后将其转换为结构以显示不同的部分。

字典采用字符串和用户对象数组：

var userByOccupation: [String: [User]] = [:]

我从后端（firestore）中拉出职业，然后是用户，然后将用户附加到指定的职业。 但是，只要我设置了值和键，然后从字典中打印出值计数，它就会返回nil。

我在getUsers（）函数中遇到错误：

（请参阅最后3行也用其输出标记）

func getOccupations(){
    let db = Firestore.firestore()

    db.collection("occupations").getDocuments { (snapshot, err) in
        if let error = err {
            print("There was an error fetching documents: \(error)")
        } else {
            guard let documents = snapshot?.documents else { return }
            for document in documents {
                var occupationID = document.documentID
                db.collection("occupations").document(occupationID).collection("users").getDocuments(completion: { (secondSnapshot, error) in
                    if let err = error {
                        print("There was an error fetching documents: \(err)")
                    } else {
                        guard let secondDocuments = secondSnapshot?.documents else { return }
                        for document in secondDocuments {
                           self.getUsers(occupationID: occupationID, userID: document.documentID)
                        }
                    }
                })
            }
        }
    }
}

func getUsers(occupationID: String, userID: String) {
    let db = Firestore.firestore()
    db.collection("users").document(userID).getDocument(completion: { (snapshot, error) in
        if let err = error {
             print("There was an error fetching documents: \(err)")
        } else {
            if let dictionary = snapshot?.data() {
                let user = User(dictionary: dictionary  as [String: AnyObject])
                user.id = snapshot?.documentID
                print(occupationID) //MARK - prints: Janitor
                print(user.name) //MARK - prints: Jason
                self.userByOccupation[occupationID]?.append(user) //MARK: Setting the key & values
                print(self.userByOccupation.keys.count) //MARK - prints: nil.
            }
        }
    })
}

Answer 1

将?与self.userByOccupation[occupationID]一起使用，nil首先使该语句不起作用

self.userByOccupation[occupationID]?.append(user)

更改为

self.userByOccupation[occupationID] = [user] // or use +=

设置键和值对后，Swift字典返回nil

1 个答案: