8. Contract Lottery | Raffle

One Liner Dependencies Installation

yarn add --dev @nomiclabs/hardhat-ethers@npm:hardhat-deploy-ethers ethers @nomiclabs/hardhat-etherscan @nomiclabs/hardhat-waffle chai ethereum-waffle hardhat hardhat-contract-sizer hardhat-deploy hardhat-gas-reporter prettier prettier-plugin-solidity solhint solidity-coverage dotenv

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Contract Details

• Raffle

• Enter the lottery (paying some amount)

• Pick a random winner (verifiably random)

• Winner to be selected every X minutes -> completely automate

• Chainlink Oracle -> Randomness, Automated Execution (Chainlink Keepers)

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Events

• Whenever we update a dynamic array or mapping, we should emit an event

• Stored in the logging data structure of the EVM

• Whenever we emit an event, there are two types of parameters

  • indexed parameters / topics

    • We can have upto 3 of these

    • These are seachable

  • unindexed parameters

    • Decoded via their ABIs

    • Costs less gas

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Hardhat Shorthand

• Npm package that is installed globally as package hh

• Supports shell autocomplete

• yarn global add shorthand

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Hardhat special testing/debugging methods

https://hardhat.org/hardhat-network/docs/reference#special-testing/debugging-methods

evm_increaseTime

Allows us to increase time of the blockchain

evm_mine

Allows us to mine(create) new blocks

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Final Files

https://github.com/PatrickAlphaC/hardhat-smartcontract-lottery-fcc

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