address payable --> address
address payable addr1 = msg.sender; address addr2 = addr1; // 隱式轉 address addr3 = address(addr1); // 顯式轉
address --> address payable
address addr1 = msg.sender; address payable addr2 = address( uint160(addr1) ); // 需要先經過uint160
普通數組地址是:address[],可支付數組地址是:address payable[]