Questions tagged [require]

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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 ...
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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&...
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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; ...
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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) ...
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1answer
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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 ...
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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?
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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 ""...
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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 ...
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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) { ...
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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": "...
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0answers
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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 ...
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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 ...
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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 { ...
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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(!...
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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 ...
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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 ...
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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 ...
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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 ...
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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)(...
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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 ...
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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"....
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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 ...
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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][...
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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 ...
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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?
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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. ...
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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 ...
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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 ...
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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....
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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 ...
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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" , "...
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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 ...
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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....
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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 ...
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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?
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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 != ...
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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(...
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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 ...
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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 ...
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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, ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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) ...
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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 ...
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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). ...
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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 ...
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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() &...