This topic is about Solidity – Restricted Access.
Restricted Access to a Contract is a common practice. By Default, a contract state is read-only unless it is specified as public.
We can restrict who can modify the contract’s state or call a contract’s functions using modifiers. We will create and use multiple modifiers as explained below −
- onlyBy − once used on a function then only the mentioned caller can call this function.
- onlyAfter − once used on a function then that function can be called after certain time period.
- costs − once used on a function then caller can call this function only if certain value is provided.
Example
pragma solidity ^0.5.0;
contract Test {
address public owner = msg.sender;
uint public creationTime = now;
modifier onlyBy(address _account) {
require(
msg.sender == _account,
"Sender not authorized."
);
_;
}
function changeOwner(address _newOwner) public onlyBy(owner) {
owner = _newOwner;
}
modifier onlyAfter(uint _time) {
require(
now >= _time,
"Function called too early."
);
_;
}
function disown() public onlyBy(owner) onlyAfter(creationTime + 6 weeks) {
delete owner;
}
modifier costs(uint _amount) {
require(
msg.value >= _amount,
"Not enough Ether provided."
);
_;
if (msg.value > _amount)
msg.sender.transfer(msg.value - _amount);
}
function forceOwnerChange(address _newOwner) public payable costs(200 ether) {
owner = _newOwner;
if (uint(owner) & 0 == 1) return;
}
}
In this topic we learned about Solidity – Restricted Access. To know more, Click Here.
Pingback: Solidity - Withdrawal Pattern - Adglob Infosystem Pvt Ltd