Restrict Access to Some Functions

Most smart contracts will need access restrictions on functions that only the owner of the contract should be able to invoke. A commonly used pattern for this is the onlyOwner pattern. This is where a custom modifier requires that the caller of the function is equal to the owner address.

To save writing your own logic for this, Openzeppelin provides a contract called Ownable,

pragma solidity ^0.5.5;

import "@openzeppelin/contracts/ownership/Ownable.sol";

contract OwnableContract is Ownable {

  function restrictedFunction() public onlyOwner returns (uint) {
    return 99;
  }

  function openFunction() public returns (uint) {
    return 1;
  }

}