无法将'[NSObject：AnyObject]'类型的值转换为强制

Question

这是产生此错误的代码。

for dic: [NSObject : AnyObject] in items as! [[NSObject : AnyObject]] {
            if (dic["Value"] != nil) {
                values.append((dic["Value"] as! String))
                var dict = dic as NSMutableDictionary
                if ((dic["Details"] as! String) == "") {
                    hasValues = false
                    dict["ISRequired"] = Int(true)
                } else {
                    (dic as NSMutableDictionary)["ISRequired"] = Int(false)
                }
            }
        }

错误解释说我无法转换为可变字典。