I recently came across the following Solidity function:
function testHealthFactor() public {
(, , , , , uint256 healthFactor) = ILendingPool(lendingPool).getUserAccountData(user);
console.log("health factor", healthFactor);
assertEq(healthFactor < 1 ether, true);
}
I don't know Solidity enought yet, so I wander what is the mining of that sequence of 5 commas?
Solidity allows you to return multiple values within a function. If you don't need these values, you can omit them, and move to the next with the ,.
For example:
function returnStuff() public returns (uint256, uint256) {
return (1, 3);
}
( , uint256 ourNum) = returnStuff();
// ourNum = 3
Related
I've been following a tutorial on chainlink documentation, to get the current price of Matic using MATIC/USD Mumbai Testnet Data feed, the function getLatestPrice() returns 65990700. I read that latestRoundData() returns the value in Wei. Then when I converted it using this website https://polygonscan.com/unitconverter to see how much this value is worth of Matic. I got 0.000000000065485509 Matic.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
import "#chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract PriceConsumerV3 {
AggregatorV3Interface internal priceFeed;
/**
* Network: Mumbai
* Aggregator: MATIC/USD
* Address: 0xd0D5e3DB44DE05E9F294BB0a3bEEaF030DE24Ada
*/
constructor() {
priceFeed = AggregatorV3Interface(0xd0D5e3DB44DE05E9F294BB0a3bEEaF030DE24Ada);
}
/**
* Returns the latest price
*/
function getLatestPrice() public view returns (int) {
(
/*uint80 roundID*/,
int price,
/*uint startedAt*/,
/*uint timeStamp*/,
/*uint80 answeredInRound*/
) = priceFeed.latestRoundData();
return price;
}
}
am I missing something ?
Chainlink USD datafeeds return price data with 8 decimals precision, not 18.
If you want to convert the value to 18 decimals, you can add 10 zeros to the result:
price * 1e10
See the decimals function output on the specified feed contract.
This is my first time to write a computer programming language and it's a smart contract.
After finish, I pressed compile, and it shows the following error: DeclarationError: Identifier not found or not unique.
mapping(string=> team) teams;
^_ _^
Please anyone help me to find out what is the problem?
My smart contract as below:
// spdx-license-identifier: MIT
pragma solidity ^0.7.0;
contract Database {
struct Team {
string engineer;
mapping (string=>uint) numbers;
}
mapping(string=>team) teams;
function addTeams(string calldata teamName, string calldata engineer) public {
Team storage team = teams [teamName];
team.engineer = engineer;
}
function addDrawingNumber(string calldata teamName, string calldata engineerName, uint number) public {
Team storage team = teams [teamName];
team.numbers[engineerName] = number;
}
function getDrawingNumber(string calldata teamName, string calldata engineerName) public view returns (uint) {
Team storage team = teams [teamName];
return team.numbers[engineerName]
; }
}
Solidity is a case-sensitive language. You have defined a struct type Team (capital T) - but in the mapping you're trying to use a type team (lowercase t), which is not defined.
Solution: Unify the case sensitivity.
struct Team {
string engineer;
mapping (string=>uint) numbers;
}
mapping(string=>Team) teams;
I have a problem. The problem is that i want a max mint supply for the whitelist sale and public sale. So for example;
In total i have 10.000 NFT's. There will be an whitelist sale and a public sale. For the whitelist sale i have 2.000 wallet addresses, but i only want them to be able to mint 1.500 NFT's. and in the public sale i want the remaining 8.500 NFT's to be sold.
I already tried somethings with the normal maxsupply but can't figure it out. I want a max mint per wallet like 10 and cant seem to limit the supply to 1500 for only the whitelist
Does anyone can explain this to me or have a code example?
I don't recommend limiting your whitelist per-wallet minting amount (you want to mint out, don't you?!), but I understand the reasons why you might. I'll provide both options. All code is abbreviated for brevity sake:
*Note 1: We will be using OpenZeppelin Utilities - Counters for tracking minted progress. You can also consider using totalSupply(), however, if burned tokens are a concern totalSupply() will decrement and throw off your count, whereas Counters will not.
Note 2: This assumes you're whitelist occurs before public and that you're not also juggling a reserve count as well - additional checks and counters would be required for that.
Note 3: This covers ONLY the check for limiting whitelist; you will obviously also need additional checks for valid whitelist account, sufficient payment, etc.
Limit Whitelist Total Supply
...
import "#openzeppelin/contracts/utils/Counters.sol";
...
error ExceededWhitelistSupply();
...
using Counters for Counters.Counter;
uint256 public maxSupply = 10000;
uint256 public maxWhitelistSupply = 1500;
Counters.Counter private totalWhitelistSupply;
...
function mintWhitelist(uint256 _qty) external payable {
if ( totalWhitelistSupply.current() + _qty > maxWhitelistSupply ) revert ExceededWhitelistSupply();
for (uint256 i = 0; i < _qty; i++) {
totalWhitelistSupply.increment();
}
_mint(msg.sender, _qty, '', true);
}
Limit Wallet && Limit Whitelist Total Supply
...
import "#openzeppelin/contracts/utils/Counters.sol";
...
error ExceededWhitelistSupply();
error ExceededMaxPerWallet();
...
using Counters for Counters.Counter;
uint256 public maxSupply = 10000;
uint256 public maxWhitelistSupply = 1500;
uint256 public maxWhitelistPerWallet = 10;
Counters.Counter private totalWhitelistSupply;
mapping(address => uint256) public whitelistMintedAmount;
...
function mintWhitelist(uint256 _qty) external payable {
if ( whitelistMintedAmount[msg.sender] + _qty > maxWhitelistPerWallet ) revert ExceededMaxPerWallet();
if ( totalWhitelistSupply.current() + _qty > maxWhitelistSupply ) revert ExceededWhitelistSupply();
for (uint256 i = 0; i < _qty; i++) {
totalWhitelistSupply.increment();
}
whitelistMintedAmount[msg.sender] += _qty;
_mint(msg.sender, _qty, '', true);
}
Here, we've used mapping - good tutorial here - to track the number of NFTs that have been minted to this wallet (preferred method, as this won't be fooled by the account transferring NFTs out of the wallet and then minting more). If you want to go WAY down the rabbit hole, you can also look at trash-canning this whole approach and learn up on this approach for handling your whitelist.
Keep in mind that there are more checks and balances that you'll need to add (e.g., visualizing this in the front end of your dApp to avoid minting when they shouldn't be able to, additional validation layers in your mint functions, etc.), but this should provide you with the core pieces needed for limiting by a max wallet and max supply. I apologize for any code errors - this is my first StackOverflow answer and the short-handing and readability of the code is a bit difficult to error check.
Have a whitelistMaxSupply
Have a getMaxSupply function
Have a finishWhitelist function
Have a maxSupply
Unless whitelist finished, getMaxSupply will return whitelistMaxSupply, after finished, it will return maxSupply
Profit
There are many ways to solve your problem, this is just the first one that came to my mind
function getMaxSupply() view public returns(uint256){
if(whitelistFinished){
return maxSupply;
}
return whitelistMaxSupply;
}
function finishWhitelist() public{
whitelistFinished = true;
}
I use hardhat test my contract,contract code like this:
uint256 public investLength;
function A()external{
uint256 id = investLength++;
_a(id);
}
function _a(uint256 _Id) internal returns (address) {
require(_id != 0, 'id zero');
}
when running test,return id zero.This code doesn't seem to be working =>investLength++,this value did not change to 1;
uint256 id = investLength++;
This snippet assigns the current value of investLength (which is 0 by default) to id, and then increments investLength.
If you want to increment the investLength first, and then assign the already incremented value to id, use this expression:
uint256 id = ++investLength;
I am having issues when trying to use the Chainlink random number generator and deploying to Rinkeby. Relevant code pieces are the following:
Constructor from the importing contract (should be working fine).
// RandomNumberConsumer parameters for RINKEBY testnet
address _vrfCoordinator = 0xb3dCcb4Cf7a26f6cf6B120Cf5A73875B7BBc655B;
address _link = 0x01BE23585060835E02B77ef475b0Cc51aA1e0709;
bytes32 _keyHash = 0x2ed0feb3e7fd2022120aa84fab1945545a9f2ffc9076fd6156fa96eaff4c1311;
uint256 _fee = 0.1 * 10 ** 18; // 0.1 LINK
constructor() RandomNumberConsumer(_vrfCoordinator, _link, _keyHash, _fee) {}
RandomNumberConsumer.sol. As specified in the chainlink docs, with a few tweaks needed for my approach.
pragma solidity ^0.8.7;
import "#chainlink/contracts/src/v0.8/VRFConsumerBase.sol";
import "#openzeppelin/contracts/access/Ownable.sol";
import "hardhat/console.sol";
contract RandomNumberConsumer is VRFConsumerBase, Ownable{
// Variables
bytes32 internal s_keyHash;
uint256 internal s_fee;
uint256 private constant ROLL_IN_PROGRESS = 150;
mapping(bytes32 => address) private s_rollers;
mapping(address => uint256) private s_results;
//address vrfCoordinator = 0x3d2341ADb2D31f1c5530cDC622016af293177AE0;
//address link = 0xb0897686c545045aFc77CF20eC7A532E3120E0F1;
// Events
event DiceRolled(bytes32 indexed requestId, address indexed roller);
event DiceLanded(bytes32 indexed requestId, uint256 indexed result);
/**
* Constructor inherits VRFConsumerBase
*
* Network: Rinkeby
* Chainlink VRF Coordinator address: 0xb3dCcb4Cf7a26f6cf6B120Cf5A73875B7BBc655B
* LINK token address: 0x01BE23585060835E02B77ef475b0Cc51aA1e0709
* Key Hash: 0x2ed0feb3e7fd2022120aa84fab1945545a9f2ffc9076fd6156fa96eaff4c1311
*/
constructor(address vrfCoordinator, address link, bytes32 keyHash, uint256 fee)
VRFConsumerBase(vrfCoordinator, link){
s_keyHash = keyHash;
s_fee = fee;
}
// Functions
function rollDice(address roller) public onlyOwner returns (bytes32 requestId){
console.log("RNG Contract address",address(this));
// Checking LINK balance
require(LINK.balanceOf(address(this)) >= s_fee, "Not enough LINK in contract.");
// Checking if roller has already rolled dice since each roller can only ever be assigned to a single house. TODO: this can be changed
require(s_results[roller] == 0, "Already rolled");
// Requesting randomness
requestId = requestRandomness(s_keyHash, s_fee); // Error is happening here!
// Storing requestId and roller address
s_rollers[requestId] = roller;
// Emitting event to signal rolling of dice
s_results[roller] = ROLL_IN_PROGRESS;
emit DiceRolled(requestId, roller);
}
// fulfillRandomness is a special function defined within the VRFConsumerBase contract that our contract extends from.
// The coordinator sends the result of our generated randomness back to fulfillRandomness.
function fulfillRandomness(bytes32 requestId, uint256 randomness) override internal {
// Transform the result to a number between 0 and 100, both included. Using % as modulo
require(randomness!=0, "Modulo zero!");
uint256 d100Value = (randomness % 100) + 1; // +1 so s_results[player] can be 0 if no dice has been rolled
// Assign the transformed value to the address in the s_results mapping variable.
s_results[s_rollers[requestId]] = d100Value;
// Emit a DiceLanded event.
emit DiceLanded(requestId, d100Value);
}
// playerWins determines whether the player wins or lose the battle, based on a fixed chance (0-100)
function playerWins (address player, uint8 chance) internal view returns (bool wins){
require(s_results[player] != 0, "Player has not engaged in battle!");
require(s_results[player] != ROLL_IN_PROGRESS, "Battle in progress!");
return s_results[player] <= (chance + 1); //+1 because dice is 1-101
}
}
RNG call from the importing contract(simplified to relevant part only. _player address is working correctly).
address _player = ownerOf(_monId);
rollDice(_player);
I have the certainty that the error occurs inside the rollDice function, more specifically in the call to requestRandomness. Apart from that, I cannot seem to find why the error is hapenning, nor any references to the error message (Below agreed payment) inside any of the dependency contracts. Cannot find any references online either.
Any help is appreciated, thanks.
Below agreed payment error message comes from the sufficientLINK modifier of the VRFCoordinator.sol contract. You can see it here and here.
Double-check the constructor parameters, especially the fee value.
Also, make sure to fund your smart contract with Rinkeby LINK tokens which you can claim from the faucet.