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16 votes
Accepted

Defining constructors as functions with the same name as the contract is deprecated. Use "constructor(...) { ... }" instead

This is because of a deprecated standard. In the file, Migrations.sol, replace the line: function Migrations() public { with: constructor() public { The line of code shown just above is a ...
Vignesh Karthikeyan's user avatar
7 votes

Error while buying test ether from https://faucet.metamask.io/ - Mastering Ethereum

Don't make it so hard for you. Just use a working faucet. None of us can fix a problem with the faucet you mentioned. Here is a working Ropsten Testnet Faucet: https://faucet.ropsten.be/
cqx's user avatar
  • 3,462
4 votes

What happens to a transaction after you clicked 'send' in Ethereum network?[Transaction life cycle at the EVM and P2P networking level]?

You're missing the mining process. You should really explore it for a better understanding. Transactions will be sent to one of the nodes which will broadcast the transaction to the other(s). ...
Rob Hitchens's user avatar
  • 55.3k
2 votes

How do ethereum validate a OLD transaction(say 10k blocks ago) without sync/replay-ing the full node?

The ethereum client validates the blocks as it syncs them. If it's a fully synced node, it usually validates every block it receives. Otherwise, it does more or less checks, depending on the syncmode ...
Tudor Constantin's user avatar
1 vote

Run bot on same server as your own Ethereum node

In theory it would reduce latency and help you in getting your transactions faster to the blockchain. But in reality in 99% of use cases latency doesn't make much difference, as long as it's not ...
Lauri Peltonen's user avatar
1 vote

How a consensus algorithm is implemented in a private Blockchain network ( ethereum )?

How to implement a new custom consensus algorithm in a network? As per your question you need to first fork private ethereum blockchain(go ethereum) and need to modify consensus.go file as per ...
Mahesh Rajput's user avatar
1 vote

"Gas estimation failed" on Ropsten with Invalid RPC JSON

Make sure that you are providing some withdraw_amount in the Value datafield in Remix IDE. By default it has value as 0. Consider this answer for your reference. https://ethereum.stackexchange.com/a/...
Prachi Sharma's user avatar
1 vote

Code Example from “Mastering Ethereum: Building Smart Contracts and DApps” doesn't work

It compiles perfectly under solidity 0.4.22 but you a probably using a newer one with breaking changes. Determine your compiler version with $ truffle version You should see something like solc: 0....
Rob Hitchens's user avatar
  • 55.3k
1 vote

Can I use Flutter or Android Studio to design front end instead of using react.js and still be able to interact with ethereum?

Yes, you can, but there are not many examples out there yet. Check out these two packages: ethereum: https://pub.dartlang.org/packages/ethereum web3dart: https://pub.dartlang.org/packages/web3dart ...
Awnage's user avatar
  • 11
1 vote

Trying to figure if blockchain has finished downloading.

The best way to check is to do the following: in a separate terminal, run geth attach to attach to your node type eth.syncing to check the status. If it returns false then you are synced. If not, it ...
Shane Fontaine's user avatar
1 vote

Why does ethereum use only GPU for computation? Why mobile processing powers are not used?

Ethereum does not use or require GPU for mining (computation). GPUs just happen to be the best suited readily available components for the calculations. You can mine with your CPU but it will be ...
Lauri Peltonen's user avatar

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