Questions tagged [require]
The require tag has no usage guidance.
54
questions
0
votes
0answers
10 views
require() statement to use for including Ganache GUI in the Dapp not Canache-cli
When using ganache-cli, we assign it using the require() statement. How do we do the same for ganache GUI? I don't want to use the ganache-cli for my app execution.
Also how do I assign the provider ...
1
vote
2answers
260 views
How to get reason revert using web3.eth.call
I have a smart contract with required message and pretend to use the required/validation message in front end.
require(bytes(hashAlreadyRegistered[hash]).length == 0, "Hash already registered&...
0
votes
1answer
38 views
Mapping didn't storing unique values
I wrote this piece of code with the goal to store unique documents hash. Used mapping to accomplished that.
pragma solidity ^0.5.16;
contract DocumentHash{
string public documentHash;
...
0
votes
1answer
26 views
Could you explain what this require conditions means in this smart contract
I would like to know what exactly this require condition do in this smart contract:
function placeBet(uint betMask, uint modulo, uint commitLastBlock, uint commit, uint8 v, bytes32 r, bytes32 s) ...
0
votes
1answer
16 views
Test for Require statement in Truffle
I wrote a function that generate a key value.
the function codes is here
mapping(string => bool) processedHash;
mapping(uint => bool) HashList;
function generateHash(uint256 ...
1
vote
2answers
93 views
Read message of require / revert statement in app.js
In my App.js I have called the smart contract function and the require statement in the function is not satisfied, so how do I get the message of that require statement in my App.js?
1
vote
2answers
60 views
Correct syntax for require required
I am getting following error message with require statement:
Error: Wrong argument count for function call: 0 arguments given but
expected 1. This function requires a single bytes argument. Use ""...
0
votes
1answer
60 views
ERROR: Web3 not defined
I'm trying to build a browser UI to interact with my Solidity smart contract that is deployed on my local Ganache blockchain. But I can't seem to get my index.html file to connect to Metamask. I keep ...
0
votes
1answer
52 views
Always raising “Gas required exceeds allowance or always failing transaction” when the condition of require() is not met
I tried to run the following code to check the error message when the condition of require() is not met.
pragma solidity ^0.5.16;
...
function addUser(string memory name) public returns (int) {
...
0
votes
2answers
365 views
How to diagnose a “Error: Transaction has been reverted by the EVM”?
This the error intercepted from my javascript, using web3.js
Error: Transaction has been reverted by the EVM:
{
"blockHash": "...
1
vote
0answers
42 views
Require not working on geth private node
I have created this contract to manage a votation:
pragma solidity ^0.5.7;
contract Votacion{
mapping(uint => address[]) private votosCandidatos;
uint[] listaCandidatos;
bool abierta;
address ...
1
vote
1answer
39 views
A Way Around Restricted Getters
Consider a getter function with a restriction on who can read it, like
function getData()
public
view
returns (uint x)
{
require(msg.sender = '0x123..123');
x = data;
}
This ...
0
votes
2answers
129 views
Check if contract exists in list
I've got a contract which creates another contracts and stores them in a list. How can I check that contract with specific index already exists?
import "./User.sol";
contract Main is Ownable {
...
0
votes
1answer
37 views
How do I check If a map entry doesn't exist for a given sender?
I have a map such as:
mapping (address => bytes32) private myMap;
Later in the code, in a function, I want to ensure my sender already has an entry in that given map.
Can I do this?
require(!...
2
votes
3answers
354 views
Should I use require in view functions?
When I call a solidity function to get a struct element, is it a best practice to use require and check if the element exists or should I just return the empty values?
Without require:
function ...
0
votes
1answer
95 views
Geth Node doesn't revert a transaction not satisfying a require
i'm testing my smart contract on remix with local ganache cli, when i try to test case that doesn't satisfy a require on the SC i correctly receive message "transact to Contract.function errored: VM ...
2
votes
1answer
198 views
How to handle require/revert/assert errors properly
I'm trying to find an easy pattern to revert/rollback a write transaction.
The first idea was to log a GenericErrorEvent but then I noticed that it will never be emited if any require/revert/assert ...
1
vote
1answer
92 views
How to get require() to accept decimal value of ether in payable functions in Solidity?
On using,
require(msg.value == registerFeeMap[msg.sender] /_currentRate)
(fractional ETH value calculated)
require(msg.value == registerFeeMap[msg.sender]*10**18/ _currentRate)
(ETH converted to ...
1
vote
2answers
86 views
How to use function arguments of payable function for require statement?
function createCampaign(uint deposit, address ll) public payable{
dpst = deposit;
require(msg.value > (40*dpst)/100 wei);
address newCampaign = address((new Campaign).value(msg.value)(...
2
votes
2answers
38 views
Validate bytes16 argument size
I have a function which accepts one bytes16 argument.
function start(
bytes16 reference
)
I have some events which I use to track behaviour, using reference as the index. Everything works ...
2
votes
1answer
218 views
VM Exception while processing transaction: revert message
When a solidity smart contract reverts with a message due to a failure on a require statement, the browser calling the smart contract returns "Error: VM Exception while processing transaction: revert"....
0
votes
1answer
73 views
Is there a way to know the REAL msg.sender?
I want to know the real msg.sender of the transaction. Which this means is, if I use truffle console I can change the msg.sender by using {from: another address}. So let's say my address is A, and ...
1
vote
1answer
75 views
Why does this function not need a require statement?
Why does the following function not need a require statment?
function transferFrom(address from, address to, uint256 value) public returns (bool) {
_allowed[from][msg.sender] = _allowed[from][...
1
vote
1answer
498 views
Emit event while require statement fails
I would like to be able to log a result of a condition:
if(time > 5) {
emit Result("time is larger than 5");
} else {
emit Result("time is less than 5");
}
This will work just fine, but ...
2
votes
2answers
42 views
Does the require function need more gas when called with a message?
If I add a message to require as a second parameter, will it increase gas consumption?
0
votes
0answers
42 views
Are function modifiers added to the stack in solidity? [duplicate]
I've got a function with a decent number of modifiers and I hit the CompilerError: Stack too deep, try removing local variables error. If I remove one of the modifiers though, everything's all right.
...
1
vote
2answers
46 views
Check given adders transaction history? [closed]
I've created a voting game on eth blockchain. I would like to make a function, that only address with previous transaction history(not a fresh address) can call. So doesn't allow people to create a ...
4
votes
1answer
302 views
how accurate are gas estimates?
I am currently running some tests on ganache using web3.js connector.
Most of my transactions run OK if I supply the same amount of gas that is suggested by web3.eth.estimateGas(), however, one of ...
4
votes
1answer
148 views
Setting time requirements in Solidity
I want a function to only be able to be called after a certain specific period of time has passed from the contract's inception. Generally, I was using block.number for that. As in:
require(block....
3
votes
1answer
126 views
Access require message
I am using JavaScript to run some tests on my solidity contract. Since solidity ^0.4.22 you can have a message in require such as:
function Hello {
require(msg.sender == 0x001234, "msg.sender ...
1
vote
1answer
229 views
How to use require() with stings
I am trying to run this code on remix IDE:
pragma solidity ^0.4.24;
contract Aa {
string public result;
function feedData(string _result) public {
require(_result = "e" , "...
3
votes
1answer
37 views
Contract design by contract -> correctness and maximum gas consumption
This question is a general design question that regards contract correctness and the functions I list here are just examples.
As I develop on Ethereum, it becomes aparent to me that it might be ...
0
votes
1answer
211 views
Expect Error: transaction in Truffle [duplicate]
Im testing wheter a require function does its job by reverting and want to test in within a truffle test.
it("The URI should be unique", async () =>{
const dupURI = await token....
1
vote
1answer
607 views
Test if a map element has been deleted or does not exist?
I have a map of game IDs to game structs in my Solidity contract. I want to test if a game struct for a given ID does not exist or has been deleted. I am using the code below:
// The map that maps ...
2
votes
1answer
1k views
Custom error message in require() not showing up?
I've got Solidity v0.4.24
And I'm doing this:
require(false,"this is a test");
When I run truffle test I get the revert, but I cant see the error message.
Any ideas what could be wrong?
2
votes
2answers
2k views
Syntax: How do you require a string to be null (or anything but null)?
I want to make sure that when doSomething() is called, the string variable is always populated (that it can't be left blank):
function doSomething (string hash) public {
require(hash != ...
4
votes
2answers
527 views
Why not use require() in place of assert()?
Even though require() is used substantially more than assert(), there are places where assert() gets used.
One example would be in the widely adopted SafeMath library by OpenZeppelin:
function add(...
1
vote
2answers
55 views
transfer back msg.value to caller on error
I have a function with modifier 'payable' in the contract. My understading is, msg.value gets added to the contract's balance and then further code is executed.
First question, is this a correct ...
1
vote
1answer
250 views
Handling require/assert failure errors correctly from a Node.JS app?
I have a getter function in my smart contract that returns one of the string values in statically defined string array. Upon entry to the function, it does a bounds check on the incoming index using ...
1
vote
0answers
191 views
cannot get return variable(s) in javascript when using require in solidity
I have a function in solidity that returns a few bytes32 variables. I cannot for the life of me access those variables. Can someone please help?
function getData() public returns (bytes32, bytes32, ...
0
votes
1answer
38 views
What is an example of a require-style exception when receiving ether via a public getter?
In the Solidity documentation it is stated that:
A require-style exception is generated in the following situations:
...
If your contract receives Ether via a public getter function.
...
What is ...
1
vote
1answer
302 views
hardware and software requirements to launch an ERC20 Token
Pardon me I'm new in this.
I'm trying to launch my ERC20 token. So What are the hardware and software requirements for an ideal transfers handling server system?
1
vote
1answer
27 views
Are there any downsides to if…else logic versus rejecting in a function
Pretty much all examples of contract functions I see use the require(...) pattern. If the initial condition is not as expected, an error is thrown and the transaction is reverted.
I don't like this ...
0
votes
1answer
231 views
Why wouldn't I use require()?
CodeWars SPOILER
I'm trying to learn by doing, and I'm pretty confused. I'm working on a kata for making a coin and sending it to others. My solution fails the test because it says I'm not checking ...
0
votes
1answer
195 views
artifact.require() statement with inheritance?
Hi guys my question i very simple.
I have this contract:
B.sol
...
contract A {
...
}
contract B is A {
...
}
When i migrate to blockchain my B.sol i need to deploy every single ...
0
votes
1answer
331 views
ERC20 transfer function - Use “if, else” or “require”
Currently, I am planning to implement an ERC20 compliant transfer function in my ERC20 compliant contract as follows:
function transfer(address _to, uint256 _amount) public returns (bool success)
...
1
vote
1answer
61 views
Functions with boolean return type while using require()
I am trying to understand the reasoning for this: (for an online class)
mapping (uint => uint) public multiplier;
/**
* Called by the owner of the TollBoothOperator.
* Can be used to update a ...
0
votes
1answer
642 views
Remix Warning : Assert
I am trying to compile a contract on remix and have run into the following warning :
Use assert(x) if you never ever want x to be false, not
in any circumstance (apart from a bug in your code). ...
1
vote
4answers
2k views
Unit testing for assert()/require() in Truffle/Solidity
If I write a function like so:
function calculate(int x) public returns (int) {
require(x > 0);
// Do other stuff
return x;
}
How would I write a JavaScript unit test in Truffle ...
2
votes
1answer
1k views
Solidity multiple vs single require
One of the functions of my smart contract can only be executed if three conditions are met. At the moment I have a single require which combines all the conditions like this:
require(evalCond1() &...
