这是我的临时数据库模型

var categories: [Category] = [

            Category(name: "X",
                     sign: [Sign(code: "X-1", name: "***", description: "", picture: ""),
                            Sign(code: "X-2", name: "***", description: "", picture: "")]),
            Category(name: "Y",
                     sign: [Sign(code: "Y-1", name: "Yyy", description: "", picture: ""),
                            Sign(code: "Y-2", name: "yyy", description: "", picture: "")]),
            Category(name: "Z",
                     sign: [Sign(code: "Z-1", name: "Zzz", description: "", picture: ""),
                            Sign(code: "Z-2", name: "ZZZ", description: "", picture: "")])
                     ]

我需要从这个基中获取任意类别的一个随机元素（不是每个类别中的一个），并将其打印为sign.code
我准备了变量来存储值：
第一个月
并尝试用for循环来实现：

func randomSign() {
            for categorie in categories {
                randomSign = categorie.sign.randomElement()

但是，在结果中，我的循环从每个类别中生成随机元素，最后只保存最后一个随机元素。我想在控制台中打印例如“X-2”作为随机选择值。