When looking at sample contracts, sometimes arrays are declared in methods with "memory" and sometimes they aren't. What's the difference?

On the ethers documentation, it says that the two most commons signers are: Wallet, which is a class which knows its private key and can execute any operations with it. JsonRpcSigner, which is c...

I'm a newbie in Solidity, and I have a question about multiple inheritances. So if I have some contracts like: contract A { function foo() public virtual { console.log("A"); } } cont...

Im currently trying to use Infura to run on my machine thru Web3. When I set to run my node index.js file I get the following error: Unhandled rejection Error: This contract object doesn't have a...

I have been trying to send a transaction on the Ethereum testnet Rinkeby for the past few days and keep getting this error no matter how much I increase the gas to. "Unhandled rejection Error...

I am writing an automated test suite that needs to test functions against Uniswap v2 style automated market marker: do swaps and use different order routing. Thus, routers need to be deployed. Are ...

I tried solidity example like as above in remix, solidity version > 0.5.0 But I am getting this error now. What is the way to solve this error? contract MyContract { string value; function get(...

I'm writing unit tests using Hardhat's mainnet fork, and for a test I want to check the owner account's initial balance of an ERC20 token, in particular DAI. Here's my test so far: const { ethers }...

I'm trying to start using Ethereum Web3.js with node 6.11.1 on a macosx I installed web3 with the following command: npm install web3 Then i launch this - apparently - simple node command: ...

I came across this answer while researching creating a function for someone to buy an NFT: https://mcmap.net/q/1254039/-how-to-transfer-a-nft-from-one-account-to-another-using-erc721 The relevant l...

Problem I am trying to deploy a smart contract via Remix. Unfortunately, it fails with a very unhelpful error message. Error Message creation of MyContract errored: Error encoding arguments: Error...

How can I interact with an already deployed contract on ether(not mine) using Remix without the source code, but I have the ABI. The reason I want to do it is because some contract has more than 20...

According to official docs of ethers.js, this should be the way how to connect to a specific network like Rinkeby-testnet with custom data: const provider = ethers.getDefaultProvider(network, { e...

I am learning solidity and got to know that interface and abstract are both classes that may contain unused functions. My doubt is: What is the difference between interface and abstract contract in...

Using Solidity ^0.5.0, I'm actually trying to implement an old code working in ^0.4.17, but it throws an error on Remix. I checked syntax and everything but just can't catch what's wrong. Any help...

I am confused about how I should be executing a contract's method using the web3 1.0 library. This code works (so long as I manually unlock the account first): var contract = new web3.eth.Contrac...

I want to test my smart contract but don't know the way to access the public variables after the contact was deployed? For example: contract NFT is ERC721, Ownable { using SafeMath for uint256; bo...

I'm trying to pass the format of array of structs as argument on smart contract write function on etherscan, This is solidity example: Info[] public info; struct Info { address userAddress; uint...

I came across quite a common problem that it seems I can't solve elegantly and efficiently in solidity. I've to pass an arbitrary long array of arbitrary long strings to a solidity contract. In m...

I deployed a private network via geth and posted a smart contract there. Accounts are set in the genesis block I'm creating a python function in which I want to call a smart contract function impo...

I have deployed a ERC-1155 based contract (based on OpenZeppelin) and minted some NFTs on this contract successfully. But when I want to use these NFTs in OpenSea, it always says "Unidentified...

using web3 (python3) I am trying to decode InputData of the BSC transaction as seen on BscScan In some solutions I've found code below is being used: import web3 from web3.contract import Contract...

I've been running a local Rinkeby node (in order to use websocket events) which was working fine for a while, but suddenly I have been getting "Returned error: replacement transaction underpriced"....

fallback() external { console.log(msg.data); (bool result, ) = address(delegate).delegatecall(msg.data); if (result) { console.log("SUCESS"); this; } } returns TypeError: Member &...

I am trying to follow an older tutorial on web3, but am getting errors that I believe are due Solidity being updated. I have the following code shown below var express = require("express"), Web3 ...