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1500 questions
36
votes
2 answers
Can we get all elements stored in a mapping in the contract
Can we get all elements stored in a mapping in the contract using web3.js ?
takampika
- 385
- 1
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36
votes
1 answer
What does the keyword `super` in Solidity do?
I came across the super keyword in Solidity in the context of overriding functions. What does it do?
SCBuergel
- 8,774
- 7
- 38
- 69
36
votes
11 answers
How to get private key from account address and password?
What I have
1. I am able to create new account with personal.newAccount() method of web3 api.
2. I am working on my private blockchain.
3. geth node start with following command:-
geth --datadir ~/privateBlockChain1 --networkid 1300 --rpcport…
Imroz
- 871
- 2
- 7
- 11
36
votes
6 answers
web3: How do I get past events of myContract.myEvent?
I use the following JS code to get notified of Solidity events and it works well for incoming new events:
myContract.myEvent().watch((error, result) => {
if (error)
console.log('Error in myEvent event handler: ' + error);
else
…
SCBuergel
- 8,774
- 7
- 38
- 69
35
votes
3 answers
understanding mload assembly function
I am learning the inline assembly in solidity, I have found the function mload(0x40) I am confused with what this function does. Did it reserve 4 Slot/word in memory or did it load the data stored in the address 0X40 or what?
Sig Touri
- 1,090
- 2
- 14
- 23
35
votes
2 answers
Ethereum smart contract security checklist
Is there a tool, checklist of methodology to help reviewing smart contract security?
E.g. for each of function you review
Is there re-entry possibility and how it behaves on re-entry
How it behaves if loops run out of gas
How it behaves if stack…
Mikko Ohtamaa
- 22,269
- 6
- 62
- 127
35
votes
10 answers
How can I return struct when function is called?
I'd like to return struct type User. However, when I tried the following getUser function, it returns an error. Is there any way that struct data would be returned from a function?
Contract
struct User{
uint256 user_id;
bytes32 name;
…
Toshi
- 2,357
- 8
- 23
- 34
35
votes
3 answers
How do miners profit post-PoS, if at all, how will new miners get their start, and who will execute the EVM byte code (and why)?
I've been following the release of Casper/PoS closely, and I'm curious about a few details.
How will miners make money (even if GPUs are less valuable)? Are spare compute resources (say RAM, CPU) still somehow "usable" to create value by securing…
William
- 511
- 1
- 4
- 4
35
votes
6 answers
Is there a way to find an account's current transaction nonce?
I need to know my transaction nonce because I am doing fancy stuff with contract addresses (which are the keccak hash of my address + my transaction nonce). Is there a way to find this through the JavaScript console?
Broseph
- 695
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- 12
35
votes
7 answers
web3.eth.contract is not a function when making contract
Whenever I try and make a contract, I get:
web3.eth.contract is not a function
I'm using this code:
const path = require('path');
const fs = require('fs');
const solc = require('solc');
const Web3 = require('web3');
const web3 = new…
ErwanLent
- 541
- 1
- 4
- 10
35
votes
2 answers
How does Lisk differ from Ethereum?
Lisk is going to be a full stack DApp development framework for building and distributing decentralized applications. It's currently in the crowdfunding stage but got also added to Microsofts Blockchain-as-a-Service stack.
It advertises that you can…
q9f
- 32,913
- 47
- 156
- 395
35
votes
4 answers
workflow on signing a string with private key, followed by signature verification with public key
I know this question has been asked and answered, but while trying to get everything to work, I've come across some problems. This is what I'm trying to do:
1. take a target string 'Schoolbus'
2. use JSON with geth to eth_sign it
3. obtain v,r,s of…
shiso
- 1,036
- 1
- 10
- 12
35
votes
1 answer
What are Ethereum transaction receipts and what are they used for?
I've seen mention in a few places that blocks store transaction receipts, but I haven't really seen an explanation of what they are and why they exist.
Raiden Worley
- 453
- 1
- 4
- 4
35
votes
2 answers
What is the difference between `now` and `block.timestamp`?
My main goal is to obtain time spent between two transaction calls inside my smart-contract. I am not sure, should I depend on now or block.timestamp to obtain the most accurate time difference in between transactions.
I have call my contract's…
alper
- 8,395
- 11
- 63
- 152
35
votes
4 answers
Web3.js Get Contract Abi Knowing Only Contract Address
is there a way with web3.js to get a contract abi json, knowing only the contract address?
I cannot find anymore a link in wich they explain how to do this, in this post the guy replied telling that there is a way to do this but it's not so well…
user2548436
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