All Questions

I have created a simple token with ERC721, but etherscan not show my token name and symbol, why? this is my contract I deploy with this code Result on etherscan No token name and symbol showed, is ...

Let's suppose i have a wallet on one remote server, R-1. Is it possible to get the private key of that wallet/account and use it on different remote server R-2? I know, i can copy/paste files under ...

I'm trying to create a simple Dapp (via tutorial) which would allow me to send Ether from sender to receiver (via a contract with an address that automatically approves the transaction). The truffle ...

I am looking at web3.eth.ens library, I can see methods setText and getText, which allows you to set and get key value pairs against an ENS name. What is the purpose of this? Also is there a way to ...

I am trying to build an ethereum private network. Here is my genesis.json file { "config": { "chainId": 15, "homesteadBlock": 0, "eip155Block": 0, "eip158Block": 0 }, "nonce": "0x0000000000000042", "...

Sorry I probably create a topic that was answered multiple times but unfortunately I couldn't find a solution. I'm trying to use RPC server of Geth to send a raw transaction. I've an address with a ...

Develop a java project to connect to ethereum blockchain and until now no error has been presented, but now this error appeared:   org.web3j.protocol.exceptions.ClientConnectionException: Invalid ...

System information Geth version: 1.7.2-stable-0905eda4 OS & Version: Ubuntu 16.04 Branch, Commit Hash or Release: HEAD detached at v2.2.1 Actual behaviour and Steps to reproduce the behaviour ...

I need to add a random number function in my smart contract. Is it best to use Oraclize and e.g. random.org? It's not a lottery which means the random number generation does not require heavy security....

I'm aware of this post: Accessing a mapping within a struct via Truffle console However, it seems to me, it does not provide a clear answer. Also, my question is more generic and not just for ...

I searched for SE and google, but did not find answer to this simple doubt. If I include two transactions (state changing ones which cost gas) in same block for execution. Then my question is: will ...

I am new to react and finding issues with the front-end of the Dapp application. Especially in web3 version > web3 1.0.0 I just heard about the web3-react and I think it will be a lot easier. I ...

i am learning building Dapps. And i got to know to know about metamask. I've read about metamask is an ethereum wallet which we can use to sign Tx's without running a full node and inject web3 to ...

I am a beginner for Javascript & web3(0.20). I am using Metamask for watching allevents, and I need to get timestamp. I use getBlock.timestamp. Due to Javascript, timestamps are not inorder. I ...

Thank you for watching this topic. I'm not sure how I can withdraw my balance from multiple contracts. The situation is like this. 1)People have rights to withdraw each fund. 2)funds are stored at ...

I have an auction contract, where bidders bid with Ether then me (owner) select which offer is most suitable and thus this bidder is contract winner. Once the winner is selected, I send him data as a ...

I'm writing my first contract and my withdraw function doesnt work. Eth doesnt move to my _withdrawAddr. Also can somebody explain why my function getBalanceThis returns 0 instead of amount I send to ...

I'm dealing with goLang on an go-ethereum fork. In order to query a contract endpoint I need to get a fresh EVM reference for properly call the contract. I've found there is a NewEVM function that ...

I am reading the Web3 documentation about signing transactions (see example below). As I understand it, the "transaction object" gets turned into a hex string and enveloped, this is the "message". The ...

Can someone point me right tutorial to understand the following 1) Genesis configuration for POA with pre-fund account 2) How to add Authority account at run time means once the blockchain is up ...

Let's say I have 3 conditions which can lead to revert(). which way should I handle it? 3 types of events or one event with extra parameters? 3 events types: if condition A: emit causeA(dataA1, ...

function transfer(address _to, uint256 _value) public returns (bool success) { require(balances[msg.sender] >= _value); balances[msg.sender] -= _value; balances[_to] += _value; emit ...

I got stuck in making two contracts interact. The code for two contracts is as follows: Test1.sol pragma solidity ^0.5.8; contract Test1 { struct Car { string carCreationDate; ...

I have set up a private POA Network according to the tutorial from the parity homepage. I have two nodes running on localhost:8540 and localhost:8541. I have connected MetaMask to my first node and am ...

Is there any validation process of smart contract's write operations ?

I'm currently using the ethereumjs libraries (https://github.com/ethereumjs) to iterate over the blockchain, replay transactions and read the state trie of a contract from the geth leveldb. Currently ...

can i change the consensus algorithm for a network that has forked from github? is there any link to understand how can make changes to consensus

I am using python package py-solc-x for compiling the smart contract. os.path.abspath("D:/new.sol") Gives path where my test contract exits. 'D:\\new.sol' Then i use compile_files to compile the ...

Suppose i have a loop. Here user is a struct of which player is an address. address[] memory addrs = new address[](n); for(uint i=0;i<n;i++){ addrs[i] = user.player; } return addrs; This is a ...

How can I receive the same hash in solidity and web3? Multiple values where one is a multi dimensional array. Solidity v0.5.x: pragma solidity 0.5.6; pragma experimental ABIEncoderV2; contract Hash{...

What is the best way to verify that a text I received in mu function is a valid hash? In other words, contains a specified length and is composed only by numbers and "a", "b", "c", "d", "e" or "f"?

I have written simple function in remix. pragma solidity ^0.5.0; contract testCompile{ string myString = "Hello World"; function showString() public view returns (string memory){...

Today is June 17. but when I execute my function and store the following arguments. WriterModel(owner,postID, _postContent, now); "now", It returns the July 20 timestamp. It perfectly working fine ...

Importing web3@1.0.0-beta.55 in a stencil+typescript file for a frontend application directly triggers an error, even without using the imported Web3 object whatsoever. import Web3 from 'web3'; -> ...

I have a ERC 20 token platform the token: BTZ botztoken and what I am wanting to do is figure out what I can do with the tokens as utility tokens to accomplish teams mission which is: to help ...

I want to do a transaction (sent ether or token) by API, not from web3.js I have tried etherscan, block cypher This is a get balance API code like this I want send transaction code ...

One of the function in Contract: function getPostCounts(uint _postID)public view returns(PostCountsModel memory postCounts){ return postCountOperations[_postID]; } This is the calling ...

I've opened Chrome extension and downloaded the Brave search engine. However, even though I've selected to show MetaMask in my tool bar it's not showing anywhere and I don't know how to access it. So, ...

Whenever a ticket will be purchased, a random number will be generated function _mightWin() internal { address _player = msg.sender; // players address uint256 ...

I'm currently learning how to write smart contracts. While studying some code, I came across this line: ‭ uint256 a = value.ceil(basePercent); (with: uint256 public basePercent = 100;) Then one ...

pragma solidity ^0.5.0; contract Testing{ struct personalInfo { uint id; string[] colors; bool player; } mapping(uint=> ...

i'm trying to compile this code (from DappUniversity: https://github.com/dappuniversity/ico_irl/blob/master/contracts/DappTokenCrowdsale.sol) but with the new version of OpenZeppelin, that's use at ...

I am wondering if I can pass the mnemonic that I created using metamask to boot up my local ganache network so that I do not have to log out and login metamask with different mnemonic everytime for a ...

I want to use an iterating uint as an identifying number, but I have a simple question to make sure I can do this safely on the mainnet. Here's a simple example to demonstrate the issue: pragma ...

I have private/local network/chain setup. I'm building this with Nodejs-->expressjs. const contract = new web3.eth.Contract(abi, address); const batch = new web3.BatchRequest(); batch.add(contract....

I have some transaction that is sent and from time to time when I call the eth_getTransactionReceipt I get a null. I see esentially two approaches for handling this: I could reiterate the call to ...

What is the most cost effective way to compare to arrays eg. uint arrays in solidity. Running a for loop takes too much gas.

I am writing a contract where I am trying to save the account addresses of customers who buy an item online. I tried it with arrays but it did not work. Can anyone please suggest a way of doing this?

I am running a test which involves creating several thousand ethereum wallets. Is there any way to import the private keys of these wallets in bulk in geth or any other offline wallet?

$ truffle migrate Compiling your contracts... =========================== > Everything is up to date, there is nothing to compile. Starting migrations... ====================== > Network name: ...