All Questions

I have an array of bytes32 with various pieces of information at various byte positions in it, and 2nd 3 bytes are a number, which I convert to uint24 like so: function setData(bytes32[] memory data) ...

For educational purposes I am implementing a blockchain from scratch without the use of any frameworks. How would I go about testing my blockchain using multiple nodes when I only have access to one ...

I am writing a Medium blog post about front-running and can't seem to find information about the order of the transactions in the same block. I have executed two trades, one with the lower fee, call ...

I build ETH wallet app by using web3.js. My concept is the new ETH address will generate when user is registered on my app and when they send ETH from other address on another app or whatever to the ...

With solidity, we cannot directly calculate 0.1 or 0.001. We usually use decimal multiplier and divisor integer to calculate those numbers like this 0.01 = 1 / 100 When the number is more than 1, it ...

import React from 'react'; import ReactDOM from 'react-dom'; import Web3 from 'web3'; class App extends React.Component { componentWillMount() { this.loadBlockchainData() } ...

I am planning to move from PoW to PoA consensus (clique) using geth. But I am confused of some of the topics - 1) Empty blocks are created periodically? What is the size of an empty block? 2) Is it ...

I'm trying to write a test with ganache and truffle to create a contract instance from another contract. Everything works in Remix but it doesn't in ganache. This is the code const assert = require('...

I need to implement a token that´s minted by a process verified by 4 peers, for that I´m going to use MultiSigWallet code (GitHub) and I´ve do some changes to adapt it but the modifier "notExecuted" ...

sorry if the question is silly.... I am tying to build a simple app that checks ETH wallet addresses balances and transactions (for both ETH and Tokens). As far as my knowledge goes, I think that I ...

I'm using react and javascript. For whatever reason, I've tried a few methods and it doesn't seem to be opening metamask. await window.ethereum.enable(); and window.web3 = new Web3(web3....

So I've created a token for my Dapp. I want to have users buy tokens to vote in my app and "elect" people. I also want to use them agin in a court like system. Essentially, I want token holders to be ...

Can I tell just from the bytecode if the contract at a specific address is a library. The use case can be if I want to use an external contract with delegate call but I don't have the contract code or ...

I am learning to program Solidity and just playing around with it in remix. I am creating compiling the following code in Solidity: pragma solidity >=0.4.22 <0.6.0; contract Ballot { ...

I am sending ether to multiple accounts and I want to send them without delay or waiting for confirmation of previous transaction. const fs = require("fs"); const os = require("os"); const Web3 = ...

I would like to read the csv text file and make a transaction via web3.js like what I did with web3.py Here is my python code #!/usr/bin/python3.7 import os import time import pandas as pd from ...

So I'm looking at this example. And they the following example for how to make a PoW function. bytes32 public currentChallenge; // The coin starts with a challenge uint public timeOfLastProof; // ...

I am confused as to what is the difference between method id, event id and abi signature. I got the abi signature of a token transfer function according to the following web3js function const ...

After deploying a library using truffle, I want to compile a contract and use the library address inside its generated bytecode. Now inside the contract bytecode I get something like _DateTime______. ...

I am running geth using this command: geth -testnet --syncmode light console and I am trying to retrieve the block number from geth and display it on my web app. In geth when I type: eth....

I've been tasked with writing a blockchain-based application (probably written in JS) that can be used to certify documents. I've done some research into where I can get stuff hosted (Infura looks the ...

The error pops up whenever I try to compile through truffle, not able to figure out a solution any help is highly appreciated. Here is the error Compiling your contracts... ==========================...

There are 3 contracts; A, B, and C. C has a state variable that initialized null. A changes that state variable to Yerevan. After that, B sees that variable. Evaluating by A is successfull but B sees ...

I have 2 contracts in 1 .sol file and when I run 'truffle migrate', it tells me that it has deployed 1 of the contracts and given me an additional error: Blockquote Invalid number of parameters ...

Say I have received an ERC20 token in my address. Such address has no ETH and no other tokens except the one I just received. If I try to estimate the gas cost of sending the token from that address, ...

Truffle has many "boxes", two of which are: truffle unbox react And: truffle unbox drizzle They both seem to be focused on frontend development. Other than Drizzle being based on a Redux store, ...

Is there a way to load the truffle console with the following variables without having to do manual type-ins on every test? let app = await MyContract.deployed(); let accounts = web3.eth.getAccounts()...

I'm trying to kill this contract /** *Submitted for verification at Etherscan.io on 2016-08-31 */ //sol Wallet // Multi-sig, daily-limited account proxy/wallet. // @authors: // Gav Wood <g@...

I have a voting system and admin groups contracts. Each admin group (it contains array of addresses allowed to vote) can grab a voting contract and vote for changing code in my contracts environment. ...

I'm trying to create an api where i have to provide transaction logs in json objects but im unable to add result of replayPastTransactionsFlowable into an collection object @GetMapping("/test") ...

In my several programs which I ran through remix IDE, I got a CallData text box. I don't know what value I have to give to this Calldata text box. I tried the following: from: address : "...

I install OpenZeppelin's contracts npm install @openzeppelin/contracts Create a contract: pragma solidity ^0.5.0; import "@openzeppelin/contracts/token/ERC20/ERC20Mintable.sol"; contract NewCoin ...

I would like to know how my custom ERC721 0x marketplace can be customized. I know the FAQ has a walkthrough and I already found out how to inject my custom ERC20 token address, symbols etc. but I ...

I have a voting solidity file here: pragma solidity >=0.4.21 <0.7.0; // We have to specify what version of compiler this code will compile with contract Votingapp{ /* mapping field below is ...

A couple years ago, I bid on a domain name through the Ethereum Name Service (ENS) that is not valid, as it is considered a subdomain. For example, something like "apple.uk.eth" which should not be ...

I have a bytes32 that I plan to pack with 10 bytes3 at specific indexes without affecting the other bytes already set. So for instance if I had a bytes3 of 0xABCDEF into bytes32 at the index 3, it ...

So, I got a problem when interacting with a smart contract in geth. I have this very simple contract: pragma solidity^0.6.1; contract Simple{ uint256 public number = 1; constructor() public { ...

I have a rinkeby token, and I wanted to add "merged mining" when someone mines a block, they get awarded 0.25 of that token. function issueBlockReward() { balanceOf[block.coinbase] += 0.25; The code ...

My Truffle project is this contract that just shows Yerevan is love: pragma solidity ^0.5.12; contract TEST{ string public note="Yerevan is love"; function rep() public view returns(string memory){ ...

I am aware that the ERC20 balance is easily obtained in web3js by calling token.methods.balanceOf(ADDRESS); However, I was wondering if there are any new developments or API that can now be used ...

I have a UI thats connected to metamask The UI updates all the Info now on address change and when metamask is enabled How can i make my UI update every second? so it always shows accurate stats on ...

How to transfer erc20 token without using contract or contract abi? The below script i have used to create Signed Raw Transaction to send Ether(ETH). How can i create Signed Raw Transaction to send ...

Im trying to fetch transaction logs from ganache using web3j library to send it as an api ,is there any way where i can get all transactions from ganache quickly? @GetMapping("/test") public List&...

I am using solidity 0.5.0 when i compile code i am throwing exception as Explicit type conversion not allowed from "bytes32" to "address". code is working fine in remix IDE and my code is as ...

I was curious if metamask uses web3 for communication with eth node ? I tried google for it; showed bunch of other results but didn't precisely answered my question. Indepth answer on how metamask ...

I know 10 of 64 characters (hex) of my ethereum private key unencrypted and their positions. I also know the corresponding wallet address. Is a brute-force possible? What I am thinking of is ...

I am writing a contract where I want to transfer money (present in the contract owners account and not the contract) to an account address passed to a function in the contract. for some reason this ...

Hi all– new to building dapps. I'm working on a little web game that returns content based on what tokens you hold in your wallet. I'm used to building web apps and mobile apps, but I've never worked ...

I just wonder to know if other crypto platform (like Waves) use its main currency (eg.waves) to pay for transaction fee when a user transfer his own-created Token to other user's address (like what ...

Why would one borrow Dai instead of buying from exchange ? if i have $150 worth ether i can borrow $100 worth Dai. With 8% stability fee basically at 8% interest rate. On the other hand i can just ...