I am learning blockchain development from youtube and I was copy-pasting things but the error wont made me compile code
Code:
pragma solidity ^0.8.0;
contract simple storage {
uint256 favoriteNumber;
bool favoriteBool;
struct people
{
uint256 favoriteNumber;
string name;
}
People[]public people{
function store(uint256 _favoriteNumber) public {
favoriteNumber =_favoriteNumber;
}
}
}
The error:
ParserError: Expected ';' but got '{'
--> contracts/simplestorage.sol:14:26:
|
14 | People[]public people{
| ^
There's a bunch of stuff wrong in your code:
You have an extra } at the end
Your contract name should be 1 word, with the camel case convention
people instruct people should be capitalized
You missing a space in between People[] public people and the statement ends with a ; not { when your declaring a global variable
pragma solidity ^0.8.7;
contract SimpleStorage {
uint256 favoriteNumber;
bool favoriteBool;
struct People
{
uint256 favoriteNumber;
string name;
}
People[] public people;
function store(uint256 _favoriteNumber) public {
favoriteNumber =_favoriteNumber;
}
}
Related
Basically I have two contracts and one test file. Contract A is initialized in Contract B. Now I want to access the public variable of Contract A through the deployed Contract B in Brownie. The contract and test case are attached below:
Contract A
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract ContractA {
uint256 internal constant INITIAL_SUPPLY = 10000000;
address public emergencyAdmin;
constructor(
string memory name,
string memory symbol,
address second
) {
emergencyAdmin = tx.origin;
_mint(second, INITIAL_SUPPLY ^ decimals());
}
}
Contract B
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "../token/ContractA.sol";
contract ContractB{
ContractA public A = new ContractA("Test Token", "TEST", address(this));
uint256 public totalStakes;
constructor() {}
receive() external payable {
}
}
Test In Brownie
import pytest
from brownie import accounts, ContractB
def test_tok():
toke= ContractB({'from':accounts[0]})
print(toke.A().emergencyAdmin())
pass
As you can see I want to access the Contract A variable emergencyAdmin from the brownie test. Contract A is deployed inside Contract B, and Contract B is depolyed in the brownie test. Upon running the test, it is showing the following error message:
AttributeError: 'EthAddress' object has no attribute 'emergencyAdmin'
You are trying to create contract on wrong place.
If you want to create Contract A on contructor of B, you have to call
new ContractA("Test Token", "TEST", address(this));
Inside constructor. And then youll be able to store the ContractA variable on ContractB.
I want to make a socket between Java client
`
import java.util.*;
import java.net.*;
import java.io.*;
public class Main
{
public static void client()
{
final int port = 2003;
final String host = "localhost";
try
{
Socket soc = new Socket(host, port);
if(soc.isBound()){
System.out.println("socket binded");
}else if(soc.isConnected()){
Scanner in = new Scanner(soc.getInputStream());
System.out.println("enter msg");
String x = in.nextLine();
PrintStream p = new PrintStream(soc.getOutputStream());
p.println("#client" + x);
} else if(soc.isClosed()){
System.out.println("Closed tunnel");
System.exit(0);
soc.close();
}
}
catch (Exception e)
{
}
}
public static void main(String[] args)
{
client();
}
}
`
Its having problem allowing me to use the scanner to send msg to Python server{I dunno how to make this}
PS : am new and dunno how to make this snippets formatted
I am using Flask at the backend and ganache for my blockchain project. I am also using Metamask. My smart contract is on the remix website. And here is my contract:
pragma solidity ^0.4.21;
contract Election{
struct Candidate {
uint voteCount;
string name;
}
struct voter {
bool authorized;
bool voted;
uint vote;
}
address public owner;
string public electionName;
mapping(address => voter) public voters;
Candidate[] public candidates;
uint public totalVotes;
modifier ownerOnly() {
require(msg.sender == owner);
_;
}
constructor(string _name) public {
owner = msg.sender;
electionName = _name;
}
function addCandidate(string _name) ownerOnly public {
candidates.push(Candidate(0, _name));
}
function getNumCandidates() public view returns(uint) {
return candidates.length;
}
function authorize(address _person) ownerOnly public {
voters[_person].authorized = true;
}
function vote(uint _voteIndex) public {
require(!voters[msg.sender].voted);
require(voters[msg.sender].authorized);
voters[msg.sender].vote = _voteIndex;
voters[msg.sender].voted = true;
candidates[_voteIndex].voteCount += 1;
totalVotes += 1;
}
function end() ownerOnly public {
selfdestruct(owner);
}
}
I am facing a problem with Vote function. When I run this whole contract after deploying on the remix website it is working fine. But when I am making transaction from my flask based app there is revert error even after having the voter in Voters list. So using metamask I want to make my transaction for voting. I deploy the contract with a default account.
w3 = Web3(HTTPProvider('http://127.0.0.1:7545'))
w3.eth.defaultAccount = w3.eth.accounts[0]
contract = w3.eth.contract(address=address, abi=data["abi"])
tx_hash = contract.functions.vote(candidate_index).transact()
w3.eth.wait_for_transaction_receipt(tx_hash)
Now I want to make transactions from the account which I choose in Metamask. Because the above method is not working. Is there any way or any example to do it? I also visited metamask documentation where the use of ethereum.request() is suggested. But I was unable to implement it in web3py.
Your code is correct. There are 2 require statements in vote. I think that is why you are getting the error. You can add custom message to require functions so you can see which one is causing the error:
require(!voters[msg.sender].voted,"You already voted");
require(voters[msg.sender].authorized,"You are not authorized");
I believe since you already call vote with your default account, you are not passing the first require statement.
Using PyZMQ to set up a client Socket connection in Unity.
The server is responding with a JSON Object which is converted to a String before sending using the Python json.dumps() method
My question is should the JSON Object be converted to a String BEFORE sending it to the client or left as a JSON Object?
Right now I am receiving
"{\"timestamp\": 1233456,\"foo\": 2,\"nofoo\": 0,\"foo_count\": 234,\"nofoo_count\": 12}"
which makes it difficult to parse.
You have C# tagged, so parsing this message in C# (dotnet core 3.1) should just be
using System.Text.Json.Serialization;
var data = "{\"timestamp\": 1233456,\"foo\": 2,\"nofoo\": 0,\"foo_count\": 234,\"nofoo_count\": 12}";
var jsonData = JsonSerializer.Deserialize<MyData>(data);
Where your POCO just looks like:
class MyData
{
public int timestamp { get; set; }
public int foo { get; set; }
public int nofoo { get; set; }
public int foo_count { get; set; }
public int nofoo_count { get; set; }
}
How can I use a StreamSocket in a Windows 8 Metro app to connect to a Python+OpenSSL-based server using a self-signed certificate in the server ? I've tried adding the server's public key to the various trusted stores on the Windows Desktop to no avail. Everything I've tried yields the same results: an exception with the same message as in this post.
I'm developing with Visual Studio 2013 on Windows 8.1, connecting to a Python 3.4 server running OpenSSL 1.0.1h
I was able to find the answer. Microsoft provides a sample here. Once you download the sample, check out scenario 5. Based on the code in that scenario, here's a Windows 8 App Store unit test class that provides an example of how to use the code:
namespace Services.Implementation.Tests
{
using System;
using System.Diagnostics;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Text;
using Windows.Networking;
using Windows.Networking.Sockets;
using Windows.Storage.Streams;
using Microsoft.VisualStudio.TestPlatform.UnitTestFramework;
using Windows.Security.Cryptography.Certificates;
using System.Collections.Generic;
[TestClass]
public class NetworkConnectionIPv6Tests
{
#region Test Lifecycle Members
/// <summary>
/// Gets or sets the test context.
/// </summary>
/// <value>
/// The test context.
/// </value>
public TestContext TestContext
{
get; set;
}
#endregion // Test Lifecycle Members
#region Test Methods
[TestMethod, TestCategory("Integration")]
public void TestConnection()
{
const int ServerPort = 63253;
const string ServerIpAddress = "fe80::7ed1:c3ff:fed9:6fc7";
HostName hostName = new HostName(ServerIpAddress);
byte[] receiveBuffer = new byte[4096];
using (StreamSocket streamSocket = new StreamSocket())
{
bool retry = true;
do
{
try
{
streamSocket.ConnectAsync(hostName, ServerPort.ToString(), SocketProtectionLevel.Tls12).GetAwaiter().GetResult();
string certInformation = GetCertificateInformation(
streamSocket.Information.ServerCertificate,
streamSocket.Information.ServerIntermediateCertificates);
Debug.WriteLine("Certificate information: {0}", certInformation);
retry = false;
}
catch (Exception exception)
{
// If this is an unknown status it means that the error is fatal and retry will likely fail.
if (SocketError.GetStatus(exception.HResult) == SocketErrorStatus.Unknown)
{
throw;
}
// If the exception was caused by an SSL error that is ignorable we are going to prompt the user
// with an enumeration of the errors and ask for permission to ignore.
if (streamSocket.Information.ServerCertificateErrorSeverity != SocketSslErrorSeverity.Ignorable)
{
Debug.WriteLine("Connect failed with error: " + exception.Message);
Assert.Fail("Failed to avoid unignorable errors");
}
// ---------------------------------------------------------------------------
// WARNING: Only test applications may ignore SSL errors.
// In real applications, ignoring server certificate errors can lead to MITM
// attacks (while the connection is secure, the server is not authenticated).
// ---------------------------------------------------------------------------
streamSocket.Control.IgnorableServerCertificateErrors.Clear();
foreach (var ignorableError in streamSocket.Information.ServerCertificateErrors)
{
streamSocket.Control.IgnorableServerCertificateErrors.Add(ignorableError);
}
}
} while (retry);
byte[] messageBytes = Encoding.UTF8.GetBytes("Test");
Stopwatch stopwatch = Stopwatch.StartNew();
uint bytesSent = streamSocket.OutputStream.WriteAsync(messageBytes.AsBuffer()).GetAwaiter().GetResult();
Assert.AreEqual(messageBytes.Length, (int) bytesSent, "Failed to sent the correct amount of bytes");
IBuffer bytesReceived = streamSocket.InputStream.ReadAsync(receiveBuffer.AsBuffer(), (uint) receiveBuffer.Length, InputStreamOptions.None).GetAwaiter().GetResult();
stopwatch.Stop();
Debug.WriteLine("Remote call turnaround in {0} seconds", stopwatch.Elapsed.TotalSeconds);
Assert.IsTrue(bytesReceived.Length > 0, "There were no bytes received from the server");
string responseString = new string(Encoding.UTF8.GetChars(receiveBuffer, 0, (int) bytesReceived.Length));
Assert.AreEqual("Test right back", responseString, "Failed to receive the expected message from the server");
}
}
#endregion // Test Methods
#region Helper Methods
/// <summary>
/// Gets detailed certificate information
/// </summary>
/// <param name="serverCert">The server certificate</param>
/// <param name="intermediateCertificates">The server certificate chain</param>
/// <returns>A string containing certificate details</returns>
private string GetCertificateInformation(
Certificate serverCert,
IReadOnlyList<Certificate> intermediateCertificates)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("\tFriendly Name: " + serverCert.FriendlyName);
sb.AppendLine("\tSubject: " + serverCert.Subject);
sb.AppendLine("\tIssuer: " + serverCert.Issuer);
sb.AppendLine("\tValidity: " + serverCert.ValidFrom + " - " + serverCert.ValidTo);
// Enumerate the entire certificate chain.
if (intermediateCertificates.Count > 0)
{
sb.AppendLine("\tCertificate chain: ");
foreach (var cert in intermediateCertificates)
{
sb.AppendLine("\t\tIntermediate Certificate Subject: " + cert.Subject);
}
}
else
{
sb.AppendLine("\tNo certificates within the intermediate chain.");
}
return sb.ToString();
}
#endregion // Helper Methods
}
}
The key to using this example is that you have to be using Visual Studio 2013 targeting for Windows 8.1.