我的代码有问题，它告诉我“无法分配给属性：'detailDic'是一个'let'常量”，我的构建失败

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "detail" {
            if let indexPath = self.tableView.indexPathForSelectedRow {
                let dic = cities[indexPath.row]
                let detailVC = segue.destination as! DetailViewController
                detailVC.detailDic = dic
                
                
            }
        }
    }

我试过这个，得到这个错误“运算符'=='的结果未使用”，它运行，但它会崩溃

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "detail" {
            if let indexPath = self.tableView.indexPathForSelectedRow {
                let dic = cities[indexPath.row]
                let detailVC = segue.destination as! DetailViewController
                detailVC.detailDic == dic
                
                
            }
        }
    }