All Questions

0
votes
0answers
4 views

solidity project using truffle

I do not know what the issue try to run truffle
1
vote
1answer
9 views

When do you use ganache-cli and when do you use ganache-core?

I have seen two usages over the internet 1. const ganache = require("ganache-cli"); web3.setProvider(ganache.provider()); 2. const ganache = require("ganache-core"); web3.setProvider(ganache....
0
votes
1answer
15 views

Is this logic possible?

Lets suppose here are user A and smartcontract B and C. A has no token but little ETH for gas, but B has enough tokens(Erc20). A send TX to B B send delegatecall to C C receive tokens in B and give ...
1
vote
1answer
12 views

How does a Truffle migration know the address of a contract before it is created?

How does the truffle migration of this contract know what the address is of the registry contract, in the constructor: https://github.com/marbleprotocol/humanity/blob/master/contracts/Humanity.sol ...
0
votes
1answer
19 views

Is a contract verified and safe if it's created by a verified contract?

The contract source code is not verified as you can see in the picture, but the contract was created by another contract code which is verified. Does that mean that the contract code from the picture ...
-2
votes
0answers
16 views

How cryptocurrency can change the world? [on hold]

My question is, in real world we earn physical paper money by doing some work like job, working in shop, doctor, lawyer and etc. etc. then we get value of it in term of physical paper or coin money ...
1
vote
1answer
14 views

Getting the transaction hash on function call

I am new to Solidity, Web3, and Ethereum. I am trying to build a web application through which users can upload a file to IPFS, then store the IPFS hash in the blockchain. I am using the React truffle ...
0
votes
0answers
12 views

How to sign a txn using web3 (1.0) and nodejs?

Firstly I know this has been asked before, but I have became confused with so many different formats and the move to 1.0. Many online resources do not make it clear about the version and I have become ...
0
votes
0answers
14 views

Infura websocket API timing out on connect

Has anyone ever had issues with the Infura Websocket API suddenly ceasing to respond. I have been using it to subscribe to event logs, but now the connection to the API is timing out.
-1
votes
0answers
13 views

Compiling Solidity contract I am getting Error

While executing this code (compiledCode = solc.compile(code)) in Command Prompt, I am getting '{"errors":[{"component":"general","formattedMessage":"* Line 1, Column 1\n Syntax error: value, ...
0
votes
0answers
26 views

How do I overcome the problem of gas limit?

Here is my genesis.json file { "config": { "chainId": 1994, "homesteadBlock": 0, "eip155Block": 0, "eip158Block": 0, "byzantiumBlock": 0 }, "...
0
votes
1answer
22 views

Private Company Network

I've got some questions regarding coonecting 2 ethereum nodes (geth) between two different networks: e.g. company A and company B. First, I've already connected two different nodes within the same ...
0
votes
0answers
10 views

How to access my wallet with a mnemonic phrase in mycrypto.com desktop app?

So here is the case: I downloaded mycrypto.com desktop app and created a mnemonic phrase there. After typing in the phrase it allows to choose a wallet from many different wallet numbers (addresses ...
-2
votes
0answers
18 views

Why do I get this error when I type “truffle migrate”?

I made a smart contract and then while I am trying to deploy it I find this. Here is the exact output I am getting. I have already made changes in the truffle-config.js file. Compiling your contracts....
0
votes
1answer
19 views

Does nonce same for all node?

Suppose in blockchain network we have 5 nodes and we have new transaction done by first node of network, so now rest of 4 node will mine the transaction to commit it in blockchain network, will the ...
1
vote
0answers
11 views

filter blocks by time range on https://etherscan.io/

Could you please tell me how I can filter the blocks by its created time on https://etherscan.io/? For example, if I want to find all blocks that were created between May-22-2019 04:50:00 AM +UTC and ...
0
votes
1answer
11 views

How we can integrate truffle with Jenkins?

is it possible to add truffle on Jenkins pipeline?
0
votes
1answer
19 views

Transaction completion in Ethereum smart contract

How can I calculate the deployment time and completion time of a smart contract transaction using web3.js?
0
votes
0answers
13 views

Is it possible user make use of tokens in certain smart contract? [on hold]

Lets suppose a certain smart contract and it has tokens(erc20) in its account. In this contract, transfer function is coded already. Is it possible user make use of tokens in this smart contract with ...
0
votes
2answers
16 views

etherscan verification problem

For some purpose. I use web3.js 0.20 to deploy contracts.(eg. press button to deploy contracts automatically, not through remix IDE). When I deploy contracts, etherscan need to verify solidity. Is ...
0
votes
0answers
9 views

If I deposit A-tokens to contract, then contract owns A-tokens?

If I deposit A-tokens(erc20) to smartcontract, then smartcontract owns A-tokens? If so, is it possible another user send TX to the smartcontract above to interact with another smartcontract with A-...
2
votes
1answer
9 views

bn256 and Boneh-Boyen digital signature in solidity

I am looking to have a full-fledged implementation of bn256 in solidity. And Boneh-Boyen digital signature. Is there is any available built-in libraries or implementation in solidity to bn256 and ...
0
votes
0answers
16 views

Is it safe for Ethereum Alarm Clock or Aion?

Scheduling service of EAC and Aion depend on participating users. Q1) is it safe for private keys of users? Would not it be possible to track the execution of the transaction and rob the private key?...
0
votes
0answers
23 views

Proxy function clashing - what kind of danger comes exactly with it?

I read that if I am using proxy, there is a chance of function clashing. Let's say in my contract there is a function with a signature: proxyOwner() ...
0
votes
1answer
17 views

How to have to two mappings to a struct?

I have a exchange type of use case in which the customer needs access to a centralised wallet based on different access methods (eg email, apikeys, actual wallet address). I tried mapping twice to the ...
0
votes
1answer
10 views

error message ParserError: Expected ',' but got 'memory'

I have this error but I do not know what is wrong? browser/arry.sol:6:58: ParserError: Expected ',' but got 'memory' function addScore(unit24 s) public returens(unit24 []memory){ ...
0
votes
1answer
15 views

Can function calls in other contracts change states?

In Solidity, is it possible to change states via function calls in other contracts? For example, let's consider the code below, where we have three assumptions: The function test2 is defined in the ...
0
votes
0answers
12 views

Let's suppose here are 2 EOA(A and B) and 1 contract

Let's suppose here are 2 EOA(A and B) and 1 contract. A has no token, B has 10token(erc20). A approve B to spend 10token(do not consider gas) B execute 2 functions in turn following via contract in ...
1
vote
1answer
17 views

ERC721Token super._mint calls addTokenTo from the top level implementation

Based on Shawn's answer, super._mint calls addTokenTo from the top level implementation (ERC721Token). How does this work? super._mint calls _mint from ERC721BasicToken reads line addTokenTo ...
1
vote
1answer
17 views

ERC721 how does tokenOfOwnerByIndex() list tokens owned by a user?

Per eip-721, there's an optional "enumeration extension". So what I did was I called balanceOf to get the number of tokens owned by the account and called tokenOfOwnerByIndex in a loop to get each ...
0
votes
0answers
20 views

How to add smart contract functionality to my blockchain?

I am currently developing my own Blockchain in C++ to just more understand the technology. I am using the Ethereum Blockchain as an example. One of the things I already copied from Ethereum blockchain ...
3
votes
0answers
15 views

String Input of three numbers (comma seperated) doesn't work in Remix

So when I try to put in three numbers as a String in a usual setter-method, it doesn't work. Does anybody know why? function test(string memory x) public view returns(string memory){ return x; }...
0
votes
1answer
12 views

Error: Data location must be “memory” for return parameter in function, but none was given

I am unable to solve the error mentioned below. Error: Data location must be "memory" for return parameter in function, but none was given. function fromHex(string memory s) public pure returns(...
0
votes
0answers
17 views

How to handle estimate gas cost error?

I am programming a button for a transaction which shall only appear if the transaction is possible. Therefore, I am using the following code contract.methods.function(parameters) .estimateGas({...},...
0
votes
0answers
32 views

I can not make a transaction in the system Blockchain [on hold]

I am studying blockchain, found a project on github. Make all the necessary settings, the project launched, but I can not make a transaction when adding data to the system. The project is under the ...
0
votes
2answers
18 views

How to handle JSON in a smart contract?

I want to store JSON input in my Smart Contract. Like { "name":"John" } First I thought i could just handle it like a String, but it is not working because of the double quotes. Remix says, that ...
0
votes
1answer
11 views

Why Could not find artifacts for contract from any sources

I am using windows 10 with truffle and ganache-cli. I have 2 contracts file to be deployed contain interfaces of other contracts defined within the contract: Contracts: ERC721Mintable.sol Ownable ...
0
votes
1answer
9 views

Can I have a listener to cryptocurrencies / tokens reaching a specific address?

Let's say that there is an address called 0x1 There is another address called 0x2 which just released a new token called ABA. Is there a way to constantly listen for 0x1 to see if it receives ABA ...
1
vote
1answer
17 views

Where can I find public and known ERC20-Contracts from existing ICOs

In order to list real live example code for ERC20-Token and Crowdsales at a talk about Smart Contracts I'm looking for such projects? Who can recommend me the real GOOD examples out there (and not ...
0
votes
1answer
15 views

How merkle tree is used to verify transaction in blockchain

May any one give example how merkle tree is used in blockchain to verify the transaction? I confused because validation of data in ethereum is done through the proof of work where you find the nonce(...
0
votes
1answer
12 views

Geth expose eth.call only via --rpcapi

Need a way to open Geth publicly, but don't want to expose all eth methods. Need only eth.call. Using --rpcapi eth will expose all eth methods. How to expose only particular one?
0
votes
1answer
21 views

Generate wallet public and private key using web3 PHP

I am using this to get public key: https://github.com/sc0Vu/web3.php#assign-value-to-outside-scopefrom-callback-scope-to-outside-scope I am in need of to get the public and private key using PHP ...
0
votes
0answers
29 views

Web3 Cannot read property 'apply' of undefined

I'm new to dapp and trying to follow iwaldman to build an ipfs-image-dapp. Here is the repo: https://github.com/iwaldman/ipfs-image-dapp. But running yarn start gives the error Cannot read property '...
0
votes
0answers
18 views

Change params from another contract

Is it possible to change params of one contract from another? I mean: contract One { address public addr; } contract Two { function test(address oneAdd) public { One one = One(oneAdd); ...
0
votes
2answers
28 views

Compare bytes32 and string using solidity

I need to compare a bytes32 value with a string. In the below example I need to check if QRVal==QRScanVal. Eg: bytes32 QRVal="0xc59aa6848d32d073bdcaa041b2735d3e4546d0836498e30de7c4c64c50933a33"; ...
0
votes
1answer
16 views

Miner address is all zero in block

I sent a transaction in clique POA private chain and get the block via transaction hash. Why is the miner address for this transaction all zero? step 1: send a transaction > eth.sendTransaction({...
0
votes
1answer
11 views

Parse Error, Expected Pragma on remix

I am new to remix and can't figure out what is wrong with this basic function. pragma solidity ^0.5.1; contract Pie { uint256 public p; } function pie () public returns (uint256) { ...
0
votes
1answer
15 views

truffle testing enum

I am trying to test an enum value from a test. This is simplified version of the contract: pragma solidity >=0.5.0 <0.7.0; contract Foo { enum State { StateA, StateB } State ...
0
votes
3answers
28 views

Getting “Error while loading the content of <contract>.sol”

After setting up the "embark-create-react-dapp-template", I didn't see a folder for contracts. So I've created one under the root level of the project (just like in the demo). But then when I executed ...
1
vote
3answers
35 views

How data is secured on ethereum network?

Blockchain is distributed decentralized database and same data is present on every node on network so now anybody on the network can see my data, so how it is secured over blockchain network?

15 30 50 per page