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-rw-r--r--solidity.html.markdown182
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`.
-
-![Remix-add-token](images/solidity/remix-add-token.png)
-
-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.
-
-![Remix-add-token](images/solidity/copy-address.png)
-
-![Remix-add-token](images/solidity/send-link.png)
-
-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