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| -rw-r--r-- | solidity.html.markdown | 182 |
1 files changed, 22 insertions, 160 deletions
diff --git a/solidity.html.markdown b/solidity.html.markdown index 748f7a35..251e9008 100644 --- a/solidity.html.markdown +++ b/solidity.html.markdown @@ -5,7 +5,7 @@ contributors: - ["Nemil Dalal", "https://www.nemil.com"] - ["Joseph Chow", ""] - ["Bhoomtawath Plinsut", "https://github.com/varshard"] - - ["Shooter", "https://github.com/liushooter"]\ + - ["Shooter", "https://github.com/liushooter"] - ["Patrick Collins", "https://gist.github.com/PatrickAlphaC"] --- @@ -214,7 +214,8 @@ assert(c >= a); // assert tests for internal invariants; require is used for use // https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/math/SafeMath.sol -// No random functions built in, see below for using Chainlink to get random numbers. +// No random functions built in, you can get a pseduo-random number by hashing the current blockhash, or get a truely random number using something like Chainlink VRF. +// https://docs.chain.link/docs/get-a-random-number // Type casting int x = int(b); @@ -645,7 +646,6 @@ reveal(100, "mySecret"); // All data to start of time is stored in blockchain, so // anyone can observe all previous data and changes - // E. Oracles and External Data // Oracles are ways to interact with your smart contracts outside the blockchain. // They are used to get data from the real world, send post requests, to the real world @@ -663,156 +663,12 @@ reveal(100, "mySecret"); // multiple sources and delivered on-chain, and we can use it as a "data bank" // of sources. -// We will need to be on a network that has the data already loaded. -// Let's look at an example -``` -# Oracles -### Getting data from Chainlink Data Feeds - -We will be deploying to a testnet with Chainlink. This way we can get decentralized data into our smart contracts. - -**Deploy the following contract with remix to the `Kovan` testnet. If unfamiliar, reference the start of this file.** - -[Work with this code in Remix](https://remix.ethereum.org/#version=soljson-v0.6.7+commit.b8d736ae.js&optimize=false&evmVersion=null&gist=0c5928a00094810d2ba01fd8d1083581&runs=200) - -We can get the price of any asset by using the `getLatestPrice` function. You can see a list of addresses for the Kovan network from the [Chainlink Documentation](https://docs.chain.link/docs/get-the-latest-price). You can also view any other address as well. - - -```javascript -/** This example code is designed to quickly deploy an example contract using Remix. - * If you have never used Remix, try our example walkthrough: https://docs.chain.link/docs/example-walkthrough - * You will need testnet ETH and LINK. - * - Kovan ETH faucet: https://faucet.kovan.network/ - * - Kovan LINK faucet: https://kovan.chain.link/ - */ - -pragma solidity ^0.6.7; - -import "https://github.com/smartcontractkit/chainlink/blob/master/evm-contracts/src/v0.6/interfaces/AggregatorV3Interface.sol"; - -contract PriceConsumerV3 { - - AggregatorV3Interface internal priceFeed; - - /** - * Network: Kovan - * Aggregator: ETH/USD - * Address: 0x9326BFA02ADD2366b30bacB125260Af641031331 - */ - constructor() public { - priceFeed = AggregatorV3Interface(0x9326BFA02ADD2366b30bacB125260Af641031331); - } - - /** - * Returns the latest price - */ - function getLatestPrice() public view returns (int) { - ( - uint80 roundID, - int price, - uint startedAt, - uint timeStamp, - uint80 answeredInRound - ) = priceFeed.latestRoundData(); - return price; - } -} - -``` - -### Randomness / RNG - -Chainlink VRF (Verifiable Random Function) is a provably-fair and verifiable source of randomness designed for smart contracts. Randomness is difficult in blockchain, because blockchains are determanistic. We can get a random number by reaching outside the blockchain to an oracle. - -Chainlink VRF then cryptographically guarantees that the random number returned is random. +// You can see other examples making API calls here: +// https://docs.chain.link/docs/make-a-http-get-request -**Deploy the following contract with remix to the `Kovan` testnet. If unfamiliar, reference the start of this file.** +// And you can of course build your own oracle network, just be sure to know +// how centralized vs decentralized your application is. -The only additional piece we need to do here is to fund our contract with LINK. [You can see a video on funding with LINK here.](https://www.youtube.com/watch?v=4ZgFijd02Jo) - -Once we deploy our Chainlink VRF contract, in order to `getRandomNumer` we need to fund the contract with LINK. Get some kovan testnet LINK [from this faucet](https://kovan.chain.link/). Once the transaction has gone through, in your metamask, hit `Add Token` and under `Custom Token` enter the address `0xa36085F69e2889c224210F603D836748e7dC0088`. - - - -NOTE: This is only the token address for Kovan. - -Once you deploy your contract, you'll need to fund it with LINK. You can fund it with link by copying your contract address from remix, and then sending that address a few LINK from your metamask. Remember this is all testnet LINK, and we can always get more for free. - - - - - -And you'll be able to work with the VRF. After deploying the content, enter a number of choice into the `getRandomNumber` function. After a delay of ~1 minute, you can hit the `randomResult` button to get the random number returned. - -```javascript -/** This example code is designed to quickly deploy an example contract using Remix. - * If you have never used Remix, try our example walkthrough: https://docs.chain.link/docs/example-walkthrough - * You will need testnet ETH and LINK. - * - Kovan ETH faucet: https://faucet.kovan.network/ - * - Kovan LINK faucet: https://kovan.chain.link/ - */ - -pragma solidity 0.6.6; - -import "https://raw.githubusercontent.com/smartcontractkit/chainlink/master/evm-contracts/src/v0.6/VRFConsumerBase.sol"; - -contract RandomNumberConsumer is VRFConsumerBase { - - bytes32 internal keyHash; - uint256 internal fee; - - uint256 public randomResult; - - /** - * Constructor inherits VRFConsumerBase - * - * Network: Kovan - * Chainlink VRF Coordinator address: 0xdD3782915140c8f3b190B5D67eAc6dc5760C46E9 - * LINK token address: 0xa36085F69e2889c224210F603D836748e7dC0088 - * Key Hash: 0x6c3699283bda56ad74f6b855546325b68d482e983852a7a82979cc4807b641f4 - */ - constructor() - VRFConsumerBase( - 0xdD3782915140c8f3b190B5D67eAc6dc5760C46E9, // VRF Coordinator - 0xa36085F69e2889c224210F603D836748e7dC0088 // LINK Token - ) public - { - keyHash = 0x6c3699283bda56ad74f6b855546325b68d482e983852a7a82979cc4807b641f4; - fee = 0.1 * 10 ** 18; // 0.1 LINK - } - - /** - * Requests randomness from a user-provided seed - */ - function getRandomNumber(uint256 userProvidedSeed) public returns (bytes32 requestId) { - require(LINK.balanceOf(address(this)) > fee, "Not enough LINK - fill contract with faucet"); - return requestRandomness(keyHash, fee, userProvidedSeed); - } - - /** - * Callback function used by VRF Coordinator - */ - function fulfillRandomness(bytes32 requestId, uint256 randomness) internal override { - randomResult = randomness; - } - - /** - * Withdraw LINK from this contract - * - * DO NOT USE THIS IN PRODUCTION AS IT CAN BE CALLED BY ANY ADDRESS. - * THIS IS PURELY FOR EXAMPLE PURPOSES. - */ - function withdrawLink() external { - require(LINK.transfer(msg.sender, LINK.balanceOf(address(this))), "Unable to transfer"); - } -} -``` - -[You can learn more about Chainlink from the documentation.](https://docs.chain.link/docs) - -You can [make API calls](https://docs.chain.link/docs/make-a-http-get-request), [set timing intervals](https://docs.chain.link/docs/chainlink-alarm-clock), and so much more. - -```javascript // Setting up oracle networks yourself // D. Cron Job @@ -869,17 +725,17 @@ Work with the full example below using the [`Javascript VM` in remix here.](http // ** START EXAMPLE ** // CrowdFunder.sol -pragma solidity ^0.4.19; +pragma solidity ^0.6.6; /// @title CrowdFunder /// @author nemild contract CrowdFunder { // Variables set on create by creator address public creator; - address public fundRecipient; // creator may be different than recipient + address payable public fundRecipient; // creator may be different than recipient, and must be payable uint public minimumToRaise; // required to tip, else everyone gets refund string campaignUrl; - byte constant version = 1; + byte version = "1"; // Data structures enum State { @@ -889,7 +745,7 @@ contract CrowdFunder { } struct Contribution { uint amount; - address contributor; + address payable contributor; } // State variables @@ -919,10 +775,10 @@ contract CrowdFunder { _; } - function CrowdFunder( + function crowdFund( uint timeInHoursForFundraising, - string _campaignUrl, - address _fundRecipient, + string memory _campaignUrl, + address payable _fundRecipient, uint _minimumToRaise) public { @@ -947,7 +803,7 @@ contract CrowdFunder { ); totalRaised += msg.value; - LogFundingReceived(msg.sender, msg.value, totalRaised); + emit LogFundingReceived(msg.sender, msg.value, totalRaised); checkIfFundingCompleteOrExpired(); return contributions.length - 1; // return id @@ -971,7 +827,7 @@ contract CrowdFunder { public inState(State.Successful) { - fundRecipient.transfer(this.balance); + fundRecipient.transfer(address(this).balance); LogWinnerPaid(fundRecipient); } @@ -1000,6 +856,7 @@ contract CrowdFunder { } } // ** END EXAMPLE ** + ``` Some more functions. @@ -1085,6 +942,11 @@ someContractAddress.callcode('function_name'); - [Modular design strategies for Ethereum Contracts](https://docs.erisindustries.com/tutorials/solidity/) - [Chainlink Documentation](https://docs.chain.link/docs/getting-started) +## Smart Contract Development Frameworks +- [Hardhat](https://hardhat.org/) +- [Brownie](https://github.com/eth-brownie/brownie) +- [Truffle](https://www.trufflesuite.com/) + ## Important libraries - [Zeppelin](https://github.com/OpenZeppelin/openzeppelin-contracts): Libraries that provide common contract patterns (crowdfuding, safemath, etc) - [Chainlink](https://github.com/smartcontractkit/chainlink): Code that allows you to interact with external data |