176 lines
3.8 KiB
Plaintext
176 lines
3.8 KiB
Plaintext
_section: Quick Start
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_subsection: Connecting to Ethereum: Metamask
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The quickest and easiest way to experiment and begin
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developing on Ethereum is to use [[link-metamask]],
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which is a browser extension that provider:
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- A connection to the Ethereum network
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- Holds your private key and can sign thing
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_code: Connecting to Metamask
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// A Web3Provider wraps a standard Web3 provider, which is
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// what Metamask injects into every page you visit as window.ethereum
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const provider = new ethers.providers.Web3Provider(window.ethereum)
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// The Metamask plugin also allows signing transactions to send ether
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// and pay to change state within the blockchain. For this, we need
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// the account signer...
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const signer = provider.getSigner()
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_heading: Querying the Blockchain
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Once you have a [[Provider]], you have a read-only connection to the
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blockchain, which can be used to query the current state, fetch historic
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logs, look up deployed code and so on.
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_code: Basic Queries
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// <hide>
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const provider = ethers.getDefaultProvider();
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// </hide>
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// Look up the current block number
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provider.getBlockNumber()
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// Get the balance of an account (by address or ENS name)
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provider.getBalance("ethers.eth")
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_heading: Writing to the Blockchain
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Every write costs ... etc
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_code: Sending Ether
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// Send 1 ether to an ens name.
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const tx = signer.sendTransaction({
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to: "ricmoo.firefly.eth",
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value: ethers.utils.parseEther("1.0")
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});
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_subsection: Contracts
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_heading: Connecting to a Contract
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To connect to an contract...
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Explain ABI
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Explain meta-class and the aBI
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_code: Connecting to a Contract
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// The ERC-20 Contract ABI, which is a common contract interface
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// for tokens.
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const abi = [
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// Some simple details about the token
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"function namd() view returns (string)",
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"function symbol() view returns (string)",
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// Get the account balance
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"function balanceOf(address) view returns (uint)",
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// Send some of your tokens to someone else
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"function transfer(address to, uint amount")",
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// An event triggered whenever anyone transfers to someone else
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"event Transfer(address indexed from, address indexed to, uint amount)"
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];
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const contract = new ethers.Contract(address, abi, provider);
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const contract = new ethers.Contract(address, abi, provider);
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_heading: Read-Only Methods
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_code: Querying the DAI Contract
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// <hide>
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// </hide>
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const contract = new Contract("dai.tokens.ethers.eth", abi, provider);
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contract.name()
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//!
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contract.symbol()
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//!
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contract.balanceOf("ricmoo.firefly.eth")
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//!
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_heading: State Changing Methods
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_heading: Listening to Events
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_code: Listening to Events
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// <hide>
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const contract = ...
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// </hide>
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// Receive an event when ANY transfer occurs
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contract.on("Transfer", (from, to, amount, event) => {
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console.log(`${ from } sent ${ formatEther(amount) } to ${ to}`);
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});
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// Receive an event when a specific address receives a token
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const filter = contract.filters.Transfer(null, address)
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contract.on(filter, (from, to, amount, event) => {
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// The to will always be "address"
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console.log(`I got ${ formatEther(amount) } from ${ from }.`);
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});
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_heading: Listing Historic Events
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_code: Historic Events by Name
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// List all transfers from anyone to anyone in the first XXX
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contract.queryFilter("Transfer", 0, XXX)
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//!
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_code: Filtering Historic Events
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// <hide>
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const contract = ...
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// </hide>
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const address = signer.getAddress()
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// Filter for all token transfers we've sent
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const filterFrom = contract.filter.Transfer(address, null);
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// <hide>
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filterFrom
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// </hide>
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//!
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// Filter for all token transfers we've received
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const filterTo = contract.filter.Transfer(null, address);
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// <hide>
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filterTo
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// </hide>
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//!
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// List all transfers we've sent between ...
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contract.queryFilter(filterFrom, 0, 100000)
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//!
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// List all transfers we've received in blockhash XXX
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contract.queryFilter(filterTo, XXX)
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//!
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_subsection: Signing Messages
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