I'm studying Solidity and I couldn't understand what does [!] mean in ⑨⑫⑬.
What does it mean? And, how to use it?
Could you give any advice, please?
function sendReward(uint256 _reward, address _dest, uint256 _id) external
onlyOwner {
require(!rewardSent[_id]); // ⑨
require(_reward > 0); // ⑩
require(address(this).balance >= _reward); // ⑪
require(_dest != address(0)); // ⑫
require(_dest != owner); // ⑬
rewardSent[_id] = true; // ⑨
_dest.transfer(_reward);
emit RewardSent(_dest, _reward, _id);
}
According to the documentation !=
is the inequality operator. The following lines all evaluate to true
:
1 == 1
1 != 2
1 != 3
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.