Latest questions in Blockchain

0 votes
1 answer

Store contract results tag in a variable

then() takes a function as argument that is ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 547 views
0 votes
1 answer

Ethereum: functions Burn and Transfer source

This statement is used to publish an event that ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 2,193 views
0 votes
1 answer

Etheruem: Unable to import library in Remix IDE

Your link is broken. This is the ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 1,783 views
0 votes
1 answer

Creating an account with web3.js v0.2.6

The answer is let a=web3.personal.newAccount('!@superpassword') H ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 826 views
0 votes
1 answer

How to allow request from host machine and deny from other machine, using ethereum in docker?

You can restrict access to the port ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 856 views
0 votes
1 answer

Nodejs Express: Getting different output in console.log and callback

If your getOrderStatus() function is like this: function getOrderStatus(_orderId, callback) ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 606 views
0 votes
1 answer

I am not able to change array elements globally

Remove the constant modifier from getArray(). constant functions do not write state ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 818 views
0 votes
1 answer

Truffle Compile failing, ParserError: Expected token LParen got Identifier function

Your parentheses are mismatched. pragma solidity ^0.4.17; import "truffle/Assert.sol"; import ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 2,657 views
0 votes
1 answer

Getting “web3.eth.filter is not a function” while trying to monitor Ethereum blocks

It appears you are using web3.js v1.0. ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 2,829 views
0 votes
1 answer

Solidity ParserError: Expected identifier but got '='

Hey, the solidity grammar doesn't allow assignments ...READ MORE

Oct 9, 2018 in Blockchain by Omkar
 • 69,220 points • 9,913 views
0 votes
1 answer

truffle migrate Error

testrpc Check your truffle.js config port and ip ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 1,396 views
0 votes
1 answer

How can I inject and use this javascript library (web3) with JavascriptCore

The web3.js library has dependencies on bignumber.js and crypto-js.js (See dependencies here). You will ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 1,065 views
0 votes
1 answer

Get specific JSON data value using array from Coin Market Cap API

use inArray function. example: $.getJSON("//api.coinmarketcap.com/v1/ticker/?limit=0", function(data) { ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 2,036 views
0 votes
1 answer

How to choose which function is called first in Node Js

You can do something like: infuraProvider.getBlockNumber().then(function(blockNumber) { ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 716 views
0 votes
1 answer

javascript bytes32 to string

Assuming you're using web3 on the JS side, it's web3.toAscii. Example ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 3,417 views
0 votes
1 answer

pubToAddress method from ethereumjs-util throws AssertionError: false == true

This code works fine: var keythereum = require('keythereum'); var ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 1,390 views
0 votes
1 answer

What is the difference between creating a new solidity contract with and without the `new` keyword?

You cannot omit new keyword for creating ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 1,313 views
0 votes
1 answer

Ethereum, web3, Error: invalid argument 0: cannot unmarshal non-string as hex data, when I call a contract

I have the same problem. But with ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 2,154 views
0 votes
1 answer

Solidity different token price

Yes you can do this by modifying ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 991 views
0 votes
1 answer

Sending hash in function parameter

I am developing a smart contract using ...READ MORE

Oct 8, 2018 in Blockchain by Omkar
 • 69,220 points • 977 views
0 votes
1 answer

How can I deploy a hyperledger business network using docker-compose?

If you want to use Composer, be ...READ MORE

Oct 4, 2018 in Blockchain by Perry
 • 17,100 points • 1,574 views
0 votes
1 answer

How to define the path to hyperledger-fabric chaincode?

You can find that in docker-compose files ...READ MORE

Oct 4, 2018 in Blockchain by Perry
 • 17,100 points • 1,533 views
0 votes
1 answer

Contract deployment is raising gas issue while transaction and issue vary on various networksbl

Starting time can't be in the past. new ...READ MORE

Oct 3, 2018 in Blockchain by Omkar
 • 69,220 points • 864 views
0 votes
1 answer

Error when Installing Ethereum: Package 'ethereum' has no installation candidate

It seems that there is a compatibility ...READ MORE

Oct 3, 2018 in Blockchain by digger
 • 26,740 points • 979 views
0 votes
1 answer

Web is not injected by metamask

You need to do import the Web3 ...READ MORE

Oct 3, 2018 in Blockchain by slayer
 • 29,370 points • 1,071 views
0 votes
1 answer

Truffle migrate fails due to missing function, but it exists in node_modules

deployer.deploy(password1, password2, deadline, {value: 100, from: accounts[0]}); ...READ MORE

Oct 3, 2018 in Blockchain by digger
 • 26,740 points • 2,202 views
0 votes
1 answer

Access variables through auto-generated getters from a different contract

You just need to pass it in ...READ MORE

Oct 3, 2018 in Blockchain by slayer
 • 29,370 points • 642 views
0 votes
1 answer

Handling UI when a trasaction is in pending (MetaMask)

You need to use the state of ...READ MORE

Oct 3, 2018 in Blockchain by digger
 • 26,740 points • 1,190 views
0 votes
1 answer

Error when trying to deploy Ethereum smart contract using web3j

Create a new credential based on the Credentials.create ...READ MORE

Oct 3, 2018 in Blockchain by slayer
 • 29,370 points • 1,736 views
0 votes
1 answer

What happens to Ether in a smart contract after selfdestruct?

selfdestruct takes one argument an address and then sends all ...READ MORE

Oct 3, 2018 in Blockchain by digger
 • 26,740 points • 1,307 views
0 votes
1 answer

Truffle migration error (test rpc is running)

1) Run the following command: npm install -g ...READ MORE

Oct 3, 2018 in Blockchain by slayer
 • 29,370 points • 868 views
0 votes
1 answer

How do display all the events logs from a smart contract?

You'll need to watch the events. const filter ...READ MORE

Oct 3, 2018 in Blockchain by digger
 • 26,740 points • 3,378 views
0 votes
1 answer

How do I initialize an array in a struct

You need to manually change the length ...READ MORE

Oct 1, 2018 in Blockchain by Perry
 • 17,100 points • 3,204 views
0 votes
1 answer

Cannot find package “google/protobuf”

Firstly, your import is wrong, you are ...READ MORE

Oct 1, 2018 in Blockchain by Perry
 • 17,100 points • 3,659 views
0 votes
2 answers

Modifiers in solidity

pragma solidity ^0.4.17; contract ModifiersTutorial { ...READ MORE

Oct 12, 2018 in Blockchain by Pulkit
 • 2,268 views
0 votes
1 answer

How to make Observable from callback?

RxJS includes a bindNodeCallback observable creator specifically for creating ...READ MORE

Oct 1, 2018 in Blockchain by digger
 • 26,740 points • 2,764 views
0 votes
1 answer

How to fix browser/IERC20.sol:4:53: Warning: This declaration shadows an existing declaration

I believe the issue is the reuse ...READ MORE

Oct 1, 2018 in Blockchain by slayer
 • 29,370 points • 1,596 views
0 votes
1 answer

Why is (startingBalance - endBalance) > (gasUsed * gasPrice) for an Ethereum transaction?

startingBalance and endBalance are BigNumber objects. Change ...READ MORE

Oct 1, 2018 in Blockchain by digger
 • 26,740 points • 1,012 views
0 votes
1 answer

Web3j: Writing operations on a contract always throw “java.lang.ArrayIndexOutOfBoundsException”

That exception is thrown when you pass ...READ MORE

Oct 1, 2018 in Blockchain by slayer
 • 29,370 points • 787 views
0 votes
1 answer

Send all Tokens and Eth to a Address automatically

require(token.transfer(beneficiary, token.balanceOf(this))); where token is the ERC20 token you're transferring. ...READ MORE

Oct 1, 2018 in Blockchain by digger
 • 26,740 points • 4,477 views
0 votes
1 answer

Ethereum client-go RPC response 403 “invalid host specified”

Adding --rpcvhosts=* should solve the issue READ MORE

Oct 1, 2018 in Blockchain by slayer
 • 29,370 points • 2,164 views
0 votes
1 answer

How to call function in one contract from another contract in private blockchain?

Please check whether you have byzantiumBlock: 0 in your ...READ MORE

Oct 1, 2018 in Blockchain by digger
 • 26,740 points • 1,002 views
0 votes
1 answer

web3.eth.sendSignedTransaction() always return “Returned error: nonce too low”

This bit of code looks wrong: var rawTx ...READ MORE

Oct 1, 2018 in Blockchain by slayer
 • 29,370 points • 6,311 views
0 votes
1 answer

Solidity mocha : address is not a contract error

Try the following: // Initialize contract variable with ...READ MORE

Oct 1, 2018 in Blockchain by digger
 • 26,740 points • 1,282 views
0 votes
1 answer

Add Peers does not add a peer in Geth console

Setup actual boot node, don't treat base ...READ MORE

Sep 28, 2018 in Blockchain by slayer
 • 29,370 points • 3,104 views
0 votes
1 answer

Invalid method parameters for eth_sendTransaction

params needs to be an array, try {"jsonrpc":"2.0","method":"eth_se ...READ MORE

Sep 28, 2018 in Blockchain by digger
 • 26,740 points • 2,089 views
0 votes
1 answer

NodeJS POST Request Over JSON-RPC

You're missing the --header option: curl --request POST \ ...READ MORE

Sep 28, 2018 in Blockchain by digger
 • 26,740 points • 2,500 views
0 votes
1 answer

How to run Meteor insert within a Fiber?

Just replace events.watch(function(error, event) { ... }); with events.watch(Meteor.bindEnvironment(function(error, event) ...READ MORE

Sep 28, 2018 in Blockchain by slayer
 • 29,370 points • 954 views
0 votes
1 answer

How to get value from solidity contract using java?

web3j caters for this very use case. It ...READ MORE

Sep 28, 2018 in Blockchain by slayer
 • 29,370 points • 2,207 views
0 votes
1 answer

Etheruem: Pyethereum Error

Try running this: sudo easy_install -U setuptools In my ...READ MORE

Sep 28, 2018 in Blockchain by digger
 • 26,740 points • 581 views
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