modifier contains (string memory what, string memory where) { bytes memory whatBytes = bytes (what); bytes memory whereBytes = bytes (where); require(whereBytes.length >= whatBytes.length); bool found = false; for (uint i = 0; i <= whereBytes.length - whatBytes.length; i++) { bool flag = true; for (uint j = 0; j < whatBytes.length; j++) if (whereBytes [i + j] != whatBytes [j]) { flag = false; break; } if (flag) { found = true; break; } } require (found); _;
}
function foo (string memory str) public contains ("solidity", str) { ...
}