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Results tagged with require
Search options answers only
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user 19510
4
votes
Accepted
Is there a way to know the REAL msg.sender?
On a real blockchain, you can't send from whatever account you want. You can only send as an address for which you know the private key.
So "the real msg.sender" is just msg.sender. It cannot be spo …
- 28.1k
1
vote
Check if contract exists in list
I'm a little unsure of what you want, but assuming _id is unrelated to an item's position in the list and you require a way to enumerate the Users in the system, you probably need both an array and a mapping … /User.sol";
contract Main is Ownable {
User[] private _users;
mapping(uint256 => bool) userExists;
function createUser(uint256 _id) onlyOwner external {
require(! …
- 28.1k
2
votes
ERC20 transfer function - Use "if, else" or "require"
So I'd say you should indeed use require, but don't include the _amount > 0 clause. …
- 28.1k
3
votes
Accepted
How to use require() with stings
There's no built-in equality test for strings (or other arrays), so a common technique is to compare the hashes of the strings instead:
function feedData(string _result) public {
// Compare hashes
require …
- 28.1k