ChainLink Price Fee using Keepers - solidity

I am trying to use the keepers chainlink service to get the eth/usd on the Kovan test net. I deployed my contract and registered it with keepers and funded with link token. Still I am not seeing the getLatestPrice() update.
contract address: 0xA29196C270cC15cb5D758Ae3613285720e6DEEb9
Upkeep address: 0xA29196C270cC15cb5D758Ae3613285720e6DEEb9
// SPDX-License-Identifier: MIT
pragma solidity 0.8.6;
import "#chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
interface KeeperCompatibleInterface {
function checkUpkeep(bytes calldata checkData) external returns (bool upkeepNeeded, bytes memory performData);
function performUpkeep(bytes calldata performData) external;
}
contract Counter is KeeperCompatibleInterface {
AggregatorV3Interface internal priceFeed;
uint public counter; // Public counter variable
// Use an interval in seconds and a timestamp to slow execution of Upkeep
uint public immutable interval;
uint public lastTimeStamp;
constructor(uint updateInterval) {
interval = updateInterval;
lastTimeStamp = block.timestamp;
counter = 0;
priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331);
}
function getLatestPrice() public view returns (int) {
(
uint80 roundID,
int price,
uint startedAt,
uint timeStamp,
uint80 answeredInRound
) = priceFeed.latestRoundData();
return price;
}
function checkUpkeep(bytes calldata checkData) external view override returns (bool upkeepNeeded, bytes memory performData) {
upkeepNeeded = (block.timestamp - lastTimeStamp) > interval;
performData = checkData;
}
function performUpkeep(bytes calldata performData) external override {
lastTimeStamp = block.timestamp;
counter = counter + 1;
performData;
getLatestPrice();
}
}

your upkeep job would be getting called, but the problem is you're not doing anything with the getLatestPrice function. This is a view function that just returns the current feed price. If you were to add a line in your performUpkeep function to actually store the result of getLatestPrice() in a variable in the contract, then you would see that it is getting called

Related

Having errors with my "Withdraw" function in Solidity

pragma solidity ^0.8.0;
//using safe math
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/SafeMath.sol";
import "hardhat/console.sol";
contract TimeLock {
/*
Functions to implement
//deposit
//withdraw
//increase timelock
//view time left
*/
/*
need to store balance per user and time per user
*/
using SafeMath for uint;
mapping(address => uint) public balancePerUser;
mapping(address => uint) public timeLeftPerUser;
function deposit( uint amount) external payable {
if(balancePerUser[msg.sender] == 0)
{
balancePerUser[msg.sender] = balancePerUser[msg.sender].add(amount);
timeLeftPerUser[msg.sender] = timeLeftPerUser[msg.sender] + block.timestamp + 8 seconds;
}
else {
balancePerUser[msg.sender] = balancePerUser[msg.sender].add(amount);
timeLeftPerUser[msg.sender] = timeLeftPerUser[msg.sender] + 8 seconds;
}
}
function increaseTimeLock( uint timeInSeconds) public {
timeLeftPerUser[msg.sender] = timeLeftPerUser[msg.sender].add(timeInSeconds);
}
function viewTimeLeft() public view returns (uint256) {
return timeLeftPerUser[msg.sender].sub(block.timestamp);
}
function checkBalance() public view returns (uint) {
return balancePerUser[msg.sender];
}
function withdraw() public payable {
// check that the sender has ether deposited in this contract in the mapping and the balance is >0
require(balancePerUser[msg.sender] > 0, "insufficient funds");
require(block.timestamp > timeLeftPerUser[msg.sender], "lock time has not expired");
// update the balance
uint amount = balancePerUser[msg.sender];
balancePerUser[msg.sender] = 0;
// send the ether back to the sender
payable(msg.sender).transfer(amount);
}
}
I initally deposit some money using the deposit function but upon using the withdraw function I get the following error. Can
The transaction has been reverted to the initial state.
Note: The called function should be payable if you send value and the value you send should be less than your current balance.
Debug the transaction to get more information.
Would appreciate any help with the same. Thanks!

'Gas Estimation Failed' Error when trying to deploy a contract on remix to the Ganache test net

This is what the error reads:
Gas estimation errored with the following message (see below). The
transaction execution will likely fail. Do you want to force sending?
Internal JSON-RPC error. { "message": "Returned error: project ID does
not have access to archive state", "code": -32000, "data": { "stack":
"Error: Returned error: project ID does not have access to archive
state\n at Object.ErrorResponse
(/usr/local/lib/node_modules/ganache-cli/build/ganache-core.node.cli.js:55:2110625)\n
at a
(/usr/local/lib/node_modules/ganache-cli/build/ganache-core.node.cli.js:55:2108932)\n
at
/usr/local/lib/node_modules/ganache-cli/build/ganache-core.node.cli.js:55:2093154\n
at runMicrotasks ()\n at processTicksAndRejections
(internal/process/task_queues.js:95:5)", "name": "Error" } }
I have made the settings for deployment on remix:
Injected Web 3
pragma solidity ^0.5.0;
pragma experimental ABIEncoderV2;
interface Structs {
struct Val {
uint256 value;
}
enum ActionType {
Deposit, // supply tokens
Withdraw, // borrow tokens
Transfer, // transfer balance between accounts
Buy, // buy an amount of some token (externally)
Sell, // sell an amount of some token (externally)
Trade, // trade tokens against another account
Liquidate, // liquidate an undercollateralized or expiring account
Vaporize, // use excess tokens to zero-out a completely negative account
Call // send arbitrary data to an address
}
enum AssetDenomination {
Wei // the amount is denominated in wei
}
enum AssetReference {
Delta // the amount is given as a delta from the current value
}
struct AssetAmount {
bool sign; // true if positive
AssetDenomination denomination;
AssetReference ref;
uint256 value;
}
struct ActionArgs {
ActionType actionType;
uint256 accountId;
AssetAmount amount;
uint256 primaryMarketId;
uint256 secondaryMarketId;
address otherAddress;
uint256 otherAccountId;
bytes data;
}
struct Info {
address owner; // The address that owns the account
uint256 number; // A nonce that allows a single address to control many accounts
}
struct Wei {
bool sign; // true if positive
uint256 value;
}
}
contract DyDxPool is Structs {
function getAccountWei(Info memory account, uint256 marketId) public view returns (Wei memory);
function operate(Info[] memory, ActionArgs[] memory) public;
}
/**
* #dev Interface of the ERC20 standard as defined in the EIP. Does not include
* the optional functions; to access them see `ERC20Detailed`.
*/
interface IERC20 {
function balanceOf(address account) external view returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
}
contract DyDxFlashLoan is Structs {
DyDxPool pool = DyDxPool(0x1E0447b19BB6EcFdAe1e4AE1694b0C3659614e4e);
address public WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
mapping(address => uint256) public currencies;
constructor() public {
currencies[WETH] = 1;
}
modifier onlyPool() {
require(
msg.sender == address(pool),
"FlashLoan: could be called by DyDx pool only"
);
_;
}
function tokenToMarketId(address token) public view returns (uint256) {
uint256 marketId = currencies[token];
require(marketId != 0, "FlashLoan: Unsupported token");
return marketId - 1;
}
// the DyDx will call `callFunction(address sender, Info memory accountInfo, bytes memory data) public` after during `operate` call
function flashloan(address token, uint256 amount, bytes memory data)
internal
{
IERC20(token).approve(address(pool), amount + 1);
Info[] memory infos = new Info[](1);
ActionArgs[] memory args = new ActionArgs[](3);
infos[0] = Info(address(this), 0);
AssetAmount memory wamt = AssetAmount(
false,
AssetDenomination.Wei,
AssetReference.Delta,
amount
);
ActionArgs memory withdraw;
withdraw.actionType = ActionType.Withdraw;
withdraw.accountId = 0;
withdraw.amount = wamt;
withdraw.primaryMarketId = tokenToMarketId(token);
withdraw.otherAddress = address(this);
args[0] = withdraw;
ActionArgs memory call;
call.actionType = ActionType.Call;
call.accountId = 0;
call.otherAddress = address(this);
call.data = data;
args[1] = call;
ActionArgs memory deposit;
AssetAmount memory damt = AssetAmount(
true,
AssetDenomination.Wei,
AssetReference.Delta,
amount + 1
);
deposit.actionType = ActionType.Deposit;
deposit.accountId = 0;
deposit.amount = damt;
deposit.primaryMarketId = tokenToMarketId(token);
deposit.otherAddress = address(this);
args[2] = deposit;
pool.operate(infos, args);
}
}
contract Flashloan is DyDxFlashLoan {
uint256 public loan;
constructor() public payable {
(bool success, ) = WETH.call.value(msg.value)("");
require(success, "fail to get weth");
}
function getFlashloan(address flashToken, uint256 flashAmount) external {
uint256 balanceBefore = IERC20(flashToken).balanceOf(address(this));
bytes memory data = abi.encode(flashToken, flashAmount, balanceBefore);
flashloan(flashToken, flashAmount, data); // execution goes to `callFunction`
}
function callFunction(
address, /* sender */
Info calldata, /* accountInfo */
bytes calldata data
) external onlyPool {
(address flashToken, uint256 flashAmount, uint256 balanceBefore) = abi
.decode(data, (address, uint256, uint256));
uint256 balanceAfter = IERC20(flashToken).balanceOf(address(this));
require(
balanceAfter - balanceBefore == flashAmount,
"contract did not get the loan"
);
loan = balanceAfter;
// Use the money here!
}
}

LP Staking solidity contract : what rewardRate should i set?

So i'm looking for a staking contract exemple to understand and deploy for my token
I found the same logic repeating in most of the contracts which is the sythetix staking algorithm
The calculation is very clever and hard to understand,
here's the code :
// SPDX-License-Identifier: MIT
pragma solidity ^0.8;
// Hero Prime Staking v1.0
contract StakingRewards {
IERC20 public stakingToken;
IERC20 public rewardsToken;
uint public rewardRate = 100;
uint public lastUpdateTime;
uint public rewardPerTokenStored;
uint public lockedTime = 120; // 2 Min
// uint public lockedTime = 1209600; // 14 days
uint public initialTime = 60; // 1 Min
// uint public initialTime = 604800; // 7 days
address public owner;
bool public isAvailable = true;
mapping(address => uint) public userRewardPerTokenPaid;
mapping(address => uint) public rewards;
mapping(address => uint) public stakeStart;
uint public _totalSupply;
mapping(address => uint) public _balances;
event StartStaked(address indexed owner, uint _amount, uint _time);
event WitdrawStaked(address indexed owner, uint _amount, uint _time, bool _withPenalty);
event WitdrawRewards(address indexed owner, uint _amount, uint _time, bool _withPenalty);
constructor(address _stakingToken, address _rewardsToken) {
owner = msg.sender;
stakingToken = IERC20(_stakingToken);
rewardsToken = IERC20(_rewardsToken);
}
modifier onlyOwner() {
require(msg.sender == owner);
_;
}
function transferOwnership(address _newOwner) external onlyOwner{
owner = _newOwner;
}
function pause() public onlyOwner{
isAvailable = false;
}
function unpause() public onlyOwner{
isAvailable = true;
}
function rewardPerToken() public view returns (uint) {
if (_totalSupply == 0) {
return 0;
}
return
rewardPerTokenStored +
(((block.timestamp - lastUpdateTime) * rewardRate * 1e18) / _totalSupply);
}
function earned(address account) public view returns (uint) {
return
((_balances[account] *
(rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18) +
rewards[account];
}
modifier updateReward(address account) {
rewardPerTokenStored = rewardPerToken();
lastUpdateTime = block.timestamp;
rewards[account] = earned(account);
userRewardPerTokenPaid[account] = rewardPerTokenStored;
_;
}
function changeRate(uint _newRate) public onlyOwner{
rewardRate = _newRate;
}
function stake(uint _amount) external updateReward(msg.sender) {
require(isAvailable == true, "The Staking is Paused");
_totalSupply += _amount;
_balances[msg.sender] += _amount;
stakeStart[msg.sender] = block.timestamp;
stakingToken.transferFrom(msg.sender, address(this), _amount);
emit StartStaked(msg.sender, _amount, block.timestamp);
}
function withdraw(uint256 _amount) external updateReward(msg.sender) {
require( (block.timestamp - stakeStart[msg.sender]) >= initialTime, "Not time yet" );
require(_balances[msg.sender] > 0, "You don't have any tokens Staked");
require(_balances[msg.sender] >= _amount, "You don't have enought tokens in Staking");
if((block.timestamp - stakeStart[msg.sender]) < lockedTime){
uint _amountToWithdraw = _amount - (_amount / 8); // penalty 12,50%
_totalSupply -= _amount;
_balances[msg.sender] -= _amount;
stakingToken.transfer(msg.sender, _amountToWithdraw);
emit WitdrawStaked(msg.sender, _amountToWithdraw, block.timestamp, true);
}else{
_totalSupply -= _amount;
_balances[msg.sender] -= _amount;
stakingToken.transfer(msg.sender, _amount); // without penalty
emit WitdrawStaked(msg.sender, _amount, block.timestamp, false);
}
}
function getReward() external updateReward(msg.sender) {
require( (block.timestamp - stakeStart[msg.sender]) >= initialTime, "Not time yet" );
if((block.timestamp - stakeStart[msg.sender]) < lockedTime){
uint reward = rewards[msg.sender] - (rewards[msg.sender] / 8); // penalty 12,50%
rewards[msg.sender] = 0;
rewardsToken.transfer(msg.sender, reward);
emit WitdrawRewards(msg.sender, reward, block.timestamp, true);
}else{
uint reward = rewards[msg.sender];
rewards[msg.sender] = 0;
rewardsToken.transfer(msg.sender, reward); // without penalty
emit WitdrawRewards(msg.sender, reward, block.timestamp, false);
}
}
function changeLockedTime(uint _newLockedTime) public onlyOwner{
lockedTime = _newLockedTime;
}
function changeInitialReward(uint _newInitialReward) public onlyOwner{
initialTime = _newInitialReward;
}
function getStaked(address _account) external view returns(uint){
return _balances[_account];
}
}
interface IERC20 {
function totalSupply() external view returns (uint);
function balanceOf(address account) external view returns (uint);
function transfer(address recipient, uint amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint);
function approve(address spender, uint amount) external returns (bool);
function transferFrom(
address sender,
address recipient,
uint amount
) external returns (bool);
event Transfer(address indexed from, address indexed to, uint value);
event Approval(address indexed owner, address indexed spender, uint value);
}
this contract is so clean and well done, i recommand using it.
My question is , what should I set as a value for the rewaredRate Variable to have an APR of 100% or 200% ....
how can I calculate what value to use ?
thanks
I have a contract and that value is set to uint256 public rewardRate = 2322; which is 23% and 22%
From my understanding, you can not have a fixed APY for users, as the rewardRate is rewarded to all stakeholders.
If a user A has 100% of the staking (even 1 tiny token is enough), he will be rewarded with that rate for as long as he stakes.
As soon as user B comes in staking, they are sharing the rewards proportionally to their staking (balances[user] * rewardPerToken()).
Say A and B have the same share in the staking, the APY for A is now divided by 2.
Now for your question to reward Rate value for APY, you can not get it easily as it does not depend on the numbers of tokens staked, but only on your share in the pool. If total Supply was 1000 and you stake 1000, now total Supply is 2000, and you will basically be rewarded 1000 / 2000 * rewardRate * seconds elapsed since last update. (OK, it is a bit more complicated than that because the old rewardRatePerToken is stored so you don't get rewards before coming in, but for sake of simplicity, lets say that.)
Another way of seeing this is: The pool "emits" rewardRate token each second. It will be shared among stakers.
So you will get rewardRate * your share each second.
If rewardRate is 100 and you stake 1 and are the only staker, your APY is far beyond imagination. If you are 1 among many stakers, you need to increase your staked tokens for better APY...
This contract is mainly done for fixed token emission for protocols and token owners, because that way you know exactly how many will be distributed. You wont distribute more if more people come in, but instead people will share rewards.

Change the state of a variable of a contract B from a Keeper

The purpose is to use this variable from the B contract
Im trying with delegate call but doesnt work,only works with event
ContractB.sol
// SPDX-License-Identifier: MIT
pragma solidity >0.8.0;
contract ContractB {
uint256 public tokenName = uint256(2);
event SetToken(uint256 _tokenName);
function setTokenName(uint256 _newName) external returns (uint256) {
setInternal(_newName);
}
function setInternal (uint256 _newName) public returns (uint256)
{
tokenName = _newName;
emit SetToken(tokenName);
return tokenName;
}
function getTokenName() public view returns (uint256)
{
return tokenName;
}
}
Counter.sol
//Begin
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
interface KeeperCompatibleInterface {
function checkUpkeep(bytes calldata checkData) external returns (bool upkeepNeeded, bytes memory performData);
function performUpkeep(bytes calldata performData) external;
}
contract Counter is KeeperCompatibleInterface {
uint256 public counter; // Public counter variable
// Use an interval in seconds and a timestamp to slow execution of Upkeep
//60 seconds
uint public immutable interval;
uint public lastTimeStamp; //My counter was updated
//**
address contractBAddress;
uint256 public tokenName = uint256(2);
//**
constructor(uint updateInterval,address _contractBAddress) {
interval = updateInterval;
lastTimeStamp = block.timestamp;
counter = 0;
contractBAddress=_contractBAddress;
}
function checkUpkeep(bytes calldata checkData) external view override returns (bool upkeepNeeded, bytes memory performData) {
upkeepNeeded = (block.timestamp - lastTimeStamp) > interval;
performData = checkData;
}
//When checkUpKeep its already to launch, this task is executed
function performUpkeep(bytes calldata) external override {
lastTimeStamp = block.timestamp;
counter=0;
counter = counter + 1;
(bool success, bytes memory returndata) = contractBAddress.delegatecall(
abi.encodeWithSignature("setTokenName(uint256)", counter)
);
// if the function call reverted
if (success == false) {
// if there is a return reason string
if (returndata.length > 0) {
// bubble up any reason for revert
assembly {
let returndata_size := mload(returndata)
revert(add(32, returndata), returndata_size)
}
} else {
revert("Function call reverted");
}
}
}
function getTokenName() public view returns (uint256)
{
return tokenName;
}
}
The event works perfect, but i cant change the state in ContractB.sol ...
https://kovan.etherscan.io/tx/0x7fbacd6fa79d73b3b3233e955c9b95ae83efe2149002d1561c696061f6b1695e#eventlog
The fact that the event worked perfectly is proof that Keeper did its job properly. The problem here is the delegatecall itself.
When contract A executes delegatecall to contract B, B's code is executed with contract A's storage, msg.sender and msg.value. Storage, current address and balance still refer to the calling contract (contract A), only the code is taken from the called address (contract B).
In your case, setTokenName updates ContractB's tokenName , ergo ContractB's storage slot 0. The same storage slot at Counter smart contract is uint256 public counter. When you executed delegatecall you updated the Counter’s storage (counter variable) with ContractB’s setTokenName function logic.
Since you know the ContractB’s ABI why don’t you do something like this?
pragma solidity ^0.8.0;
import "./ContractB.sol";
contract Counter is KeeperCompatibleInterface {
ContractB public contractB;
uint256 public counter;
constructor(ContractB _contractBAddress) {
contractB = _contractBAddress;
}
function performUpkeep(bytes calldata) external override {
counter = counter + 1;
contractB.setTokenName(counter);
}
}
You should use this:
ContractB contractB = ContractB(contractBAddress);
contractB.setTokenName(counter);
Documentation:
https://solidity-by-example.org/calling-contract/
Counter.sol
//Begin
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
interface KeeperCompatibleInterface {
function checkUpkeep(bytes calldata checkData) external returns (bool upkeepNeeded, bytes memory performData);
function performUpkeep(bytes calldata performData) external;
}
contract Counter is KeeperCompatibleInterface {
uint256 public counter; // Public counter variable
// Use an interval in seconds and a timestamp to slow execution of Upkeep
//60 seconds
uint public immutable interval;
uint public lastTimeStamp; //My counter was updated
//**
address public contractBAddress;
//**
constructor(uint updateInterval,address _contractBAddress) {
interval = updateInterval;
lastTimeStamp = block.timestamp;
counter = 0;
contractBAddress=_contractBAddress;
}
function checkUpkeep(bytes calldata checkData) external view override returns (bool upkeepNeeded, bytes memory performData) {
upkeepNeeded = (block.timestamp - lastTimeStamp) > interval;
performData = checkData;
}
//When checkUpKeep its already to launch, this task is executed
function performUpkeep(bytes calldata) external override {
lastTimeStamp = block.timestamp;
counter = counter + 1;
ContractB contractB = ContractB(contractBAddress);
contractB.setTokenName(counter);
}
}
ContractB.sol
contract ContractB {
uint256 public tokenName = uint256(2);
function setTokenName(uint256 _newName) external {
tokenName=_newName;
}
function getTokenName() public view returns (uint256)
{
return tokenName;
}
}

Type error: Member not found or visible in unit256

I have this crowdfunding platform that was initially using SafeMath library. And since is deprecated I'm looking for a workaround to make it compile and I'm getting a compilation error with remix in line 131:
contributions[msg.sender] = contributions[msg.sender].add(msg.value);
Here you have the whole contract code, it's a platform where you can create projects and raise funds:
// We will be using Solidity version 0.6.0
pragma solidity 0.6.0;
// Importing OpenZeppelin's SafeMath Implementation
//import 'https://github.com/OpenZeppelin/openzeppelin-solidity/contracts/math/SafeMath.sol';
//import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/mocks/SafeMathMock.sol";
//import "#openzeppelin/contracts/utils/math/SafeMath.sol";
contract Crowdfunding {
// using SafeMath for uint256;
// List of existing projects
Project[] private projects;
// Event that will be emitted whenever a new project is started
event ProjectStarted(
address contractAddress,
address projectStarter,
string projectTitle,
string projectDesc,
uint deadline,
uint goalAmount
);
/** #dev Function to start a new project.
* #param title Title of the project to be created
* #param description Brief description about the project
* #param durationInDays Project deadline in days
* #param amountToRaise Project goal in wei
*/
function startProject(
string calldata title,
string calldata description,
uint durationInDays,
uint amountToRaise
) external {
// uint raiseUntil = now.add(durationInDays.mul(1 days));
uint durationInSeconds = durationInDays * 1 days;
// Check that the result of division (inverse operation to multiplication) is the original number.
// If it's not, throw an exception, because the multiplication overflowed.
require(durationInSeconds / durationInDays == 1 days, 'Multiplication overflow');
uint raiseUntil = block.timestamp + durationInSeconds;
// Check that the result of subtraction (inverse operation to addition) is the original number.
// If it's not, throw an exception, because the addition overflowed.
require(raiseUntil - block.timestamp == durationInSeconds, 'Addition overflow');
Project newProject = new Project(msg.sender, title, description, raiseUntil, amountToRaise);
projects.push(newProject);
emit ProjectStarted(
address(newProject),
msg.sender,
title,
description,
raiseUntil,
amountToRaise
);
}
/** #dev Function to get all projects' contract addresses.
* #return A list of all projects' contract addreses
*/
function returnAllProjects() external view returns(Project[] memory){
return projects;
}
}
contract Project {
// not using SafeMath for uint256;
// Data structures
enum State {
Fundraising,
Expired,
Successful
}
// State variables
address payable public creator;
uint public amountGoal; // required to reach at least this much, else everyone gets refund
uint public completeAt;
uint256 public currentBalance;
uint public raiseBy;
string public title;
string public description;
State public state = State.Fundraising; // initialize on create
mapping (address => uint) public contributions;
// Event that will be emitted whenever funding will be received
event FundingReceived(address contributor, uint amount, uint currentTotal);
// Event that will be emitted whenever the project starter has received the funds
event CreatorPaid(address recipient);
// Modifier to check current state
modifier inState(State _state) {
require(state == _state);
_;
}
// Modifier to check if the function caller is the project creator
modifier isCreator() {
require(msg.sender == creator);
_;
}
constructor
(
address payable projectStarter,
string memory projectTitle,
string memory projectDesc,
uint fundRaisingDeadline,
uint goalAmount
) public {
creator = projectStarter;
title = projectTitle;
description = projectDesc;
amountGoal = goalAmount;
raiseBy = fundRaisingDeadline;
currentBalance = 0;
}
/** #dev Function to fund a certain project.
*/
function contribute() external inState(State.Fundraising) payable {
require(msg.sender != creator);
contributions[msg.sender] = contributions[msg.sender].add(msg.value);
currentBalance = currentBalance.add(msg.value);
emit FundingReceived(msg.sender, msg.value, currentBalance);
checkIfFundingCompleteOrExpired();
}
/** #dev Function to change the project state depending on conditions.
*/
function checkIfFundingCompleteOrExpired() public {
if (currentBalance >= amountGoal) {
state = State.Successful;
payOut();
} else if (now > raiseBy) {
state = State.Expired;
}
completeAt = now;
}
/** #dev Function to give the received funds to project starter.
*/
function payOut() internal inState(State.Successful) returns (bool) {
uint256 totalRaised = currentBalance;
currentBalance = 0;
if (creator.send(totalRaised)) {
emit CreatorPaid(creator);
return true;
} else {
currentBalance = totalRaised;
state = State.Successful;
}
return false;
}
/** #dev Function to retrieve donated amount when a project expires.
*/
function getRefund() public inState(State.Expired) returns (bool) {
require(contributions[msg.sender] > 0);
uint amountToRefund = contributions[msg.sender];
contributions[msg.sender] = 0;
if (!msg.sender.send(amountToRefund)) {
contributions[msg.sender] = amountToRefund;
return false;
} else {
currentBalance = currentBalance.sub(amountToRefund);
}
return true;
}
/** #dev Function to get specific information about the project.
* #return Returns all the project's details
*/
function getDetails() public view returns
(
address payable projectStarter,
string memory projectTitle,
string memory projectDesc,
uint256 deadline,
State currentState,
uint256 currentAmount,
uint256 goalAmount
) {
projectStarter = creator;
projectTitle = title;
projectDesc = description;
deadline = raiseBy;
currentState = state;
currentAmount = currentBalance;
goalAmount = amountGoal;
}
}
The Using X for Y expression extends the Y datatype with functions of the X library.
In case of using SafeMath for uint256, it allows to use the functions defined in SafeMath (such as add()) on uint256 variables.
Specifically, function add() in SafeMath checks whether the addition would overflow the 256bit unsigned integer. If it did overflow, it throws an exception. If it didn't overflow, it returns the result of the addition.
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, "SafeMath: addition overflow");
return c;
}
You can achieve the same result with this snippet:
uint256 contribution = contributions[msg.sender] + msg.value; // c = a + b
require(contribution >= contributions[msg.sender]); // require(c >= a)
contributions[msg.sender] = contribution; // return c
If you switch to Solidity 0.8+, this is not needed, because since version 0.8.0, Solidity performs the overflow check automatically and reverts if an overflow/underflow would occur. So it would be sufficient to use just this snippet:
// safe in Solidity 0.8+, unsafe in older versions
contributions[msg.sender] += msg.value;
Arithmetic operations revert on underflow and overflow. You can use unchecked { ... } to use the previous wrapping behaviour.
Source: docs