All Questions

I am trying to figure out what is wrong with the following code as it does deploy successfully on remix. pragma solidity ^0.5.11; contract MyContract { // Storage address contractOwner; ...

I want to retrieve and assign the value of my contract state variable to my javascript variable.I am doing as per guidlines provided on this community, but failed to assigned. my javascript code is ...

For example, I want to grab the current borrow rate for a token on compound.finance. In this contract InterestRateModel.sol, is there a way to call getBorrowRate from my own contract and get the ...

I have 4 nodes private ethereum. After work 2 years, 1 node suddently has over 80% disk of usage and the rest of nodes only 50 disk of usuage. Please explain for me, what's happen?

function payMe() payable{ // doing some stuff with `msg.value` users[msg.sender].balance += modifiedMsgValue ; } In the above code what if gas runs out on the second line? so there will be ...

How this protocol works, simple explain. How to do the exchange operation on this one? Best implimentation on your opinion? (subjective ofcouse)

I have some bytecode and would like to find the contract address that it belongs to. Is there an easy way to do this?

Say we have the following structure: struct MyStruct { uint256 x; uint256 y; } and that it is passed as an argument to some function. Inside that function, we have assembly block from where we ...

Scenario Suppose someone promises to deliver code to a private repository, that person is so sure they will, that they even said: "here is x eth, if I don't deliver in time, send the x eth to a ...

I have a loop like this: struct User { string name; uint tokens; uint frozenTokens; bool isValid; } mapping(address => User) users; address[] public usersAddresses; function ...

I think that I can verify a hash of a message using my signature within a Solidity contract, something like this: contract ecrecover { function testRecovery(bytes32 hash, bytes signature) returns ...

I would like to set up private chain which both geth and parity clients running on the same network. here is a sample repository with docker-compose file: https://github.com/user48736353001/devnet ...

I've my dApp running on AWS and Geth running locally. How am I supposed to connect my hosted dApp with the Geth? I'm connecting my web3(using web3.py) using my computer's(Windows OS) IP address. ...

How expensive are loops in solidity? (in terms of gas usage). I need to loop through ~1000 wallet address, and send each of them some tokens. my code: struct User { uint32 frozenAt ; uint ...

First, a student applies for a certificate in his/her University . The University creates his degree certificate . Now , how do I write a smart contract in Solidity so that anyone in blockchain can ...

I want to build stablecoin for my college project. I am thinking of developing ERC20 token pegged with fiat currency. Can someone please suggest me best tutorials/guides to build stablecoin on ERC20?

I would like to get the pending transactions in the whole network of ethereum. For example, the transaction '0xabcdefg' is right now pending in the pool, waiting to be mined by miners, after 12 ...

I first run the geth init command with the following genesis content: { "config": { "chainID": 937, "homesteadBlock": 0, "eip155Block": 0, "eip158Block": 0 }, "alloc": { "acc1": { ...

I'm trying to compile my code in Remix and I try to fix it but I keep getting the same error: Data location must be “calldata” for parameter in external function, but none was given". The problem ...

For example, a function's name and parameters are given as following: function batchTransfer(address[] _receivers, uint256 _value) public returns (bool); Then I want to get a python dictionary whose ...

I am probably doing something wrong but can't see what exactly. Code: pragma solidity ^0.5.8; import "truffle/Assert.sol"; contract TestABC { function totalSupplyTest() public { bool a ...

I wanted to revive or refactor this old smart contract as an exercise to learn solidity and js coding. Truffle compiled it and migrated it and it passed the first test (Although I'm not sure if it ...

I'm trying to perform a function that exchanges one token for another, but I'm getting a very strange bug. If I call the function in web3, I get the standard metamask popup asking whether to confirm ...

In other words, say In Python I have something like that: signed_txn = w3.eth.account.signTransaction(dict( nonce=w3.eth.getTransactionCount('0x0000000000000000000000000000000'), gasPrice = ...

modifier require(bool condition) { if (! condition) revert(); _; } When I try to truffle compile my contract I get an error here: "Warning: This declaration shadows a builtin symbol."

I was wondering if anyone knows a way of how to prove that a certain function of a solidity smart contract was executable (i.e. not reverting) after the fact without calling the function itself, e.g. ...

I want to know if it is possible to know from "error" object returned by geth that the error it was due to insufficient balance (something to compare with) I have a js code like that: mycontract....

I needed a number which could go negative but since there is no negative number in solidity this is how I'm doing it: // using safe Math uint pool = 0; // this is my number bool positivePool = true; ...

I see that there are no parallel execution in EVM. The problem I am trying to solve is the following: I have a contract which takes the input of two parties -- say users A and B. The result of the ...

I have recently started developement on Ethereum and the concepts are pretty much new to me. I need to test event emitting/listening on multiple machines for my contract. For the same, I have tried ...

Im having issues when I try to implement a back end that generate smart-contract transaction calls using web3j. But I'm a lit confused with the gas limit concept. I have defined inside the genesis ...

I'm getting the following error: TypeError [ERR_INVALID_ARG_TYPE]: The first argument must be one of type string, Buffer, ArrayBuffer, Array, or Array-like Object. Received type undefined From the ...

I want to sign a message on Remix and I can't find the pair of private/public key. For example - I going to Deploy & Run Transactions, then trying to "Sign a message using this account key" with ...

Better question: Can I send the bytes to a function that lacks this definition? In other words, say I have: event Transfer(address,address,uint256, bytes); And then: function transfer(msg....

Let's say I want to build a product that let companies settle cross-border payments for invoices using DAI (https://makerdao.com/en/dai/) as medium of exchange to ensure stable value of the ...

I fear it will be difficult for me to remember if this quirk of the language is arbitrary...

quote: To only download data from other nodes, you don't need to open any outgoing ports at all. Opening your :30303 to the world is required only if you want to run full node, helping other people ...

The execution result is at https://ropsten.etherscan.io/tx/0x92377cb678fa3f5ef19fc8f3189b76a4e3587090a6d027eab10de83fc6a07986. The following code give me "(node:2378) UnhandledPromiseRejectionWarning:...

I launch and verify an ERC20 based smart contract on a ropsten test network which allows user to interact with the contract (send eth to it and the contract automatically send token in returns as in ...

below are very simple setup of one contract calling another contract and I somehow can't get it to work. Contract C1 pragma solidity ^0.5.0; contract C1 { int public x = 1; function setX(...

Is there any incompatibility issue of solidity 0.5.12 (or perhaps ^0.5) with web3 js v1.2.2 or with Geth v1.9? Because a contract in v0.4.24 works perfectly with given web3 version and Geth version, ...

I see how uint8 can save space within a struct, but outside of that I do not see any reason to use anything but uint256. The gas cost is slightly higher for uint8. The only reason I can think of is ...

I want to determine a view function of a smart contract result in web3js 1.x Suppose we have a view function getName(uint code) and want to get the name of a person having his code. So we write: ...

If I have a struct with many customer accounts: bytes32[] public customerID; mapping(bytes32 => CustomerAccounts) public customerAccounts; struct CustomerAccounts{ address customer; uint ...

Trying to deal with ethereum contracts using openzeppelin examples and remix. There is a token contract deployed in the test network pragma solidity ^0.5.0; import "./ERC20.sol"; import "./...

I am trying to call a function from an already-deployed contract on the Ropsten network: from web3 import Web3 infura_url = "https://ropsten.infura.io/v3/XXXXXXXXXXXXXX" w3 = Web3(Web3.HTTPProvider(...

My situation is reverse to most. I am relatively experienced in coding in Solidity, but have absolutely no experience in using Python. What I would ideally like to do is have a script that will, in ...

I want to run a platform based on Ethereum and PHP to let our customers to sell/buy Ethereum based currencies online, and we have not any plan to mine the blockchain. In this regard, please help me to ...

How to get the result by parsing the log after executing the contract? How can I get the execution result ?

I have a problem connecting my url to my quorum node. I already make sure the node has an account, I run it without problem but I have that error enter image description here enter image ...