In solidity, the modifier is used to change the behavior of a function. They can automatically check a condition prior to executing the function. Here is an example, as follows:
pragma solidity ^0.4.24;
contract Modifiers {
address public admin;
function construct () public {
admin = msg.sender;
}
//define the modifiers
modifier onlyAdmin() {
// if a condition is not met then throw an exception
if (msg.sender != admin) revert();
// or else just continue executing the function
_;
}
// apply modifiers
function kill() onlyAdmin public {
selfdestruct(admin);
}
}