25 lines
496 B
Solidity
25 lines
496 B
Solidity
pragma solidity ^0.5.11;
|
|
|
|
contract Counter {
|
|
uint256 counter = 0;
|
|
string internal constant ERROR_TOO_LOW = "COUNTER_TOO_LOW";
|
|
event Changed(uint256 counter);
|
|
event Added(uint256 counter);
|
|
|
|
function add() public {
|
|
counter++;
|
|
emit Added(counter);
|
|
emit Changed(counter);
|
|
}
|
|
|
|
function subtract() public {
|
|
require(counter > 0, ERROR_TOO_LOW);
|
|
counter--;
|
|
emit Changed(counter);
|
|
}
|
|
|
|
function getCounter() public view returns (uint256) {
|
|
return counter;
|
|
}
|
|
}
|