如何在嵌套for循环中给两个数组添加数据？Firestore中scores为空怎么解决

根因分析 #

Swift中的字典为值类型，你代码中的执行顺序存在逻辑错误：

• 你先初始化了带空scores的playerData字典，直接将它的副本追加到了data["players"]数组中
• 后续内层循环修改的只是原始的playerData变量，已经存入数组的副本不会同步更新，最终提交到Firestore的数据自然就没有scores内容

修复后的代码 #

只需要调整playerData追加到数组的顺序，放在内层scores赋值完成之后执行即可：

func updateCourseData() {
    var data = ["endTime": Timestamp(date: Date()),
                "players": []] as [String : Any]

    for i in 0..<players.count {
        var playerData = ["playerId": games[i].id,
                          "scores": []] as [String : Any]

        // 先执行内层循环给scores赋值
        for score in 0..<selectedPage + 1 {
            let scoreData = ["hole": games[i].scores[score].hole,
                             "score": games[i].scores[score].score] as [String : Any]
            var existingScores = playerData["scores"] as? [[String: Any]] ?? [[String: Any]]()
            existingScores.append(scoreData)
            playerData["scores"] = existingScores
        }

        // scores赋值完成后，再把完整的playerData追加到players数组
        var existingItems = data["players"] as? [[String: Any]] ?? [[String: Any]]()
        existingItems.append(playerData)
        data["players"] = existingItems
    }

    Constants.FirebaseCollection.gamesCollection.document(documentId).updateData(data) { error in
        if let error = error {
            print(error.localizedDescription)
        }
        print("Game updated")
    }
}

内容的提问来源于stack exchange，提问作者tonileipo