All Questions

I have a storage array and I able to use push method. But, in another part of my code, I have a memory array and I can't do that. What's the reason? Doesn't exist push method in memory arrays? ...

I'm working on EVM (and more specific on hyperledger besu ethereum client) to make smart contracts more secure (by detecting and reverting malicious transactions). I need to know storage address of ...

I have already deployed contract on Ethereum. Now I want to deploy it on Ethereum 2.0, is it possible? According to some resources Ethereum 2.0 does not support for smart contract deployment. Thank ...

From what I understand, when you broadcast a transaction from a node or a service provider like Infura, it's broadcasted to other nodes and added to their mempool. Those nodes then broadcast that ...

i have problem Uncaught (in promise) TypeError: web3.fromWei(...).toNumber is not a function if I delete the code .toNumber () will be like this this my code app.js App = { web3Provider: null, ...

Can someone give me some advice on a transaction where I seem to have lost some of my tokens. I’m new to this crypto world and now I’m wondering if I got myself into something I can’t manage. I had ...

I'm quite a Noob when it comes to smart contracts, and I'm trying to design a market place. I will tokenise existing real world assets into ERC 721 tokens. The owner of each ERC721 will be eligible to ...

Flash loans enable a class of attacks that have not been possible or observed as much in prior systems. Flash minting ether is a concept that is starting to be implemented. See Example of flash ...

What do developers need to be aware of to make their contracts and systems safe against flash loans? What do they have to think about and protect against?

The WETH10 project offers a flash minting feature. This contract allows to flashMint an arbitrary amount of Wrapped Ether, unbacked by real Ether, with the condition that it is burned before the end ...

I have a test suite running in truffle, and an external web3 connected node service running - both connected to a ganache-cli network. My problem is: my tests are supposed to pick up an event ...

When I call the function myFunction in Remix IDE, it runs, however, when I call myFunction with Web3Js and React, I receive the error: Transaction has been reverted by the EVM: { "blockHash&...

I recently did a course on uDemy and get the first concepts. I'm starting to build a real-life app for a training center. I want to register in the blockchain that Jhon Doe, ID (document) xxxx, ...

I remember I saw such site when I first start learning about smart contracts last month. It is better than etherscan.io's parity trace, called function name and input are also decoded. anyone know ...

After spending hours of research, I finally found the code from this forum that will do the trick for me. I've successfully compiled the code in Remix (Kovan Test Environment), but I'm getting this ...

I'm trying to make a function that returns true if msg.sender is the owner. This is my function; function isAdmin() public view returns (bool){ require(admin == msg.sender); return true; ...

pragma solidity ^0.5.0; pragma experimental ABIEncoderV2; interface Structs { struct Val { uint256 value; } enum ActionType { Deposit, // supply tokens Withdraw, //...

Ether has precision of 10^18 which makes it impossible to use BIGINT type in database to store values in weis: DECIMAL type should be used instead. Is it worth to store values in Gwei to stay with ...

how can i get date time in solidity like that: 14/10/2020 20:50. I don't want 8:50 PM. I get in timestamp but timestamp not possible convert because I have wrong timestamp.

With web3, it is possible to call a method of a smart contract at a specific block : myContract.methods.methodName().call(transactionObject, blockNumber, callback) Is there a way to call it after a ...

I can't get the transaction to execute no matter how much I play with it. I know that it reverts during the secondary call because I always get this revert message: Timelock::executeTransaction: ...

I want to save my passwords and some other personal data on a ethereum like blockchain. it seems more persistant to me. I may lose my e-mail , my pc may crush and I may lose my usb stick. But nothing ...

I want to save my passwords and some other personal data on a ethereum like blockchain. it seems more persistant to me. I may lose my e-mail , my pc may crush and I may lose my usb stick. But nothing ...

There is a login page and register page in my dapp based on refer and earn concept to authenticate and authorize user respectively..Login part is working fine, but when I try to register a new account ...

For some reason, I cannot get any of the "Write" buttons on Etherscan to intereact with my metamask. I made sure to "connect to Web3" before I proceed to click on the "Write&...

I have a problem with collecting logs from Uniswap router contract. I use json_rpc eth_getlogs When I call the method I receive nothing. What I'm doing wrong? curl -X POST --data '{"jsonrpc":...

Let's say I deploy a voting app with web3py as the backend. Now an arbitrary user wants to cast a vote. Given that web3py cannot be integrated with metamask, what is the conventional way to detect the ...

Currently, I try to send Wrapped ETH from my account to a contract address by using IERC20. But it returned an error on Remix. By the way, I could call token.balanceOf(msg.sender) but can't execute ...

Currently the Ethereum ecosystem is showing the most adoption, by any metric - but it’s still held back by a lack of privacy for users and developers. The DeFi ecosystem on Ethereum is growing at a ...

Please excuse me even if I am not good at English. I'm interested in making ERC20 tokens these days. But I want add a function that only contractor creators can transfer the otheway. Please let me ...

I', getting to know the Ethereum technology (so rookie level). By far, with the free APIs (etherscan.io, ethplorer.io, coingecko) I have been able to build a "watch wallet". It looks like ...

I'm trying to make a game wherein I have to frequently change game opponents. Thus I need a way to define Enum participants using an external function. contract E { function setNames(string _side1, ...

I'm thinking of creating a token with a decimal point of odd number. However I'm kind of worried if there is any issue that can be caused by using an odd number for the decimal point. Is there any ...

I need update deposit when call function like that: struct Deposit { uint256 depositTime; uint256 lastDepositTime; uint256 amount; uint256 validUntil; } ...

I am trying to deploy a simple smart contract application. My target is to build something like a calculator that accepts input values from different addresses. Such addresses are pre-determined by ...

I've been stuck on this isseu for more then 24 hrs now. I have the following function in my solidity contract: function getBalance(address _addr) public view returns(uint256){ return userBalance[...

I'm trying to have a single contract that can be use as a single parent, or as multiple derived contract. Problem is both contract are overriding the same "transfer" function. Example: ...

I was trying to deploy some contracts on Rinkeby using Infura, and got the following error: Error: certificate has expired\n at TLSSocket.onConnectSecure (_tls_wrap.js:1088:34)\n at TLSSocket....

despite thinking this is an solved issue. After 1 years i have faced this issue, never met before. here is the environment; have dockerize aws ethereum instance which makes mining geth node 8545:8545 ...

1.How can I execute payable functions, like this putting the Value in the Builder console? 2.Can someone tell me the way to be able to change the address on the Buidler evm console? To execute ...

In the case of an 'invalid' transaction whereby the state transition of the execution is deemed to conflict in some way and reverts, the transaction itself is actually valid; gas is consumed, tx ...

Lately owners often say that they locked their tokens, to increase credibility. IIUC this means that they can't sell their tokens until a specific date. Where do you see this and how does it look like ...

I'm trying to create a basic ERC721 NFT, using OpenZeppelin contarct. I started with something similar to their example code: //SPDX-License-Identifier: MIT pragma solidity >=0.4.21 <0.7.0; ...

i hope life is going good bros and sisters. I am new to react native and blockchain . I am making a demo pet shop react native app (to learn mobile wallets integration with react native) ...in pet ...

I have installed the Ethereum Wallet, Ethereum-Wallet-win64-0-11-1 (zip file), as described in the book. When I start up Ethereum Wallet (testnet Ropsten, syncmode “light”) the wallet seems to load ...

I am quite new to solidity coding. I am trying to find out the best way to call complex functions like swap from 1Inch exchange smart contract from my smart contract which can execute the function by ...

I have the following function and it has been working perfectly in truffle tests as I was developing the smart contracts and now that I am implementing it in the front end I have been getting a error ...

I am trying to interact with a smart contract (the HNY token contract in particular https://blockscout.com/poa/xdai/address/0x71850b7E9Ee3f13Ab46d67167341E4bDc905Eef9/contracts) on the xDai chain. I ...

When I join the Ethereum network, I ask for block header data from neighboring nodes. How can I guarantee the reality of data？What if the neighbors conspired to give me bogus data？

Is it possible a scenario in which a malicious client executes two transactions with the same nonce of a specific account and copies and sends coins? Suppose users A, B, and C have the following ...