Mastering Blockchain Programming with Solidity

Avoid changing variable data types

The state variable data type must remain the same as the previous contract version. The data type should not be changed in the new contract version:

//Bad Practicecontract SampleContract {    uint256 public x;    bytes public y; //Data type changed}

In the preceding code, the data type of the y variable has changed from uint256 to bytes. This should be avoided.