506 lines
17 KiB
Plaintext
506 lines
17 KiB
Plaintext
_section: Getting Started @<getting-started> @priority<100>
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This is a very short introduction to Ethers, but covers many of the
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most common operations that developers require and provides a
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starting point for those newer to Ethereum.
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_heading: Getting Ethers
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If using NPM, you must first install Ethers.
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_code: installing via NPM @lang<shell>
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# Install ethers
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/home/ricmoo/test-ethers> npm install ethers
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_null:
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Everything in Ethers is exported from its root as well as on the ``ethers``
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object. There are also ``exports`` in the ``package.json`` to facilitate
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more fine-grained importing.
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Generally this documentation will presume all exports from ethers
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have been imported in the code examples, but you may import the
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necessary objects in any way you wish.
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_code: importing in Node.js @lang<script>
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// Import everything
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import { ethers } from "ethers";
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// Import just a few select items
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import { BrowserProvider, parseUnits } from "ethers";
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// Import from a specific export
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import { HDNodeWallet } from "ethers/wallet";
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_code: importing ESM in a browser @lang<script>
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<script type="module">
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import { ethers } from "https://cdnjs.cloudflare.com/ajax/libs/ethers/6.7.0/ethers.min.js";
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// Your code here...
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</script>
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_subsection: Some Common Terminology @<starting-glossary>
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To begin, it is useful to have a basic understanding of the types of
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objects available and what they are responsible for, at a high level.
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_heading: Provider
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A [[Provider]] is a read-only connection to the blockchain, which allows
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querying the blockchain state, such as account, block or transaction details,
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querying event logs or evaluating read-only code using call.
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If you are coming from Web3.js, you are used to a **Provider** offering
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both read and write access. In Ethers, all write operations are further
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abstracted into another Object, the **Signer**.
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_heading: Signer
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A [[Signer]] wraps all operations that interact with an account. An
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account generally has a private key located //somewhere//, which can be
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used to sign a variety of types of payloads.
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The private key may be located in memory (using a [[Wallet]]) or
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protected via some IPC layer, such as MetaMask which proxies interaction
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from a website to a browser plug-in, which keeps the private key out of
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the reach of the website and only permits interaction after requesting
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permission from the user and receiving authorization.
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_heading: Transaction
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To make any state changes to the blockchain, a transaction is required,
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which requires a fee to be paid, where the fee covers the associated costs
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with executing the transaction (such as reading the disk and performing
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maths) and storing the updated information.
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If a transaction reverts, a fee must still be paid, since the validator
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still had to expend resources to try running the transaction to determine
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that it reverted and the details of its failure are still be recorded.
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Transactions include sending ether from one user to another, deploying
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a **Contract** or executing a state-changing operation against a
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**Contract**.
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_heading: Contract
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A [[Contract]] is a program that has been deployed to the blockchain,
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which includes some code and has allocated storage which it can read
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from and write to.
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It may be read from when it is connected to a [[Provider]] or
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state-changing operations can be called when connected to a [[Signer]].
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_heading: Receipt
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Once a **Transaction** has been submitted to the blockchain, it is placed
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in the memory pool (mempool) until a validator decides to include it.
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A transaction's changes are only made once it has been included in the
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blockchain, at which time a receipt is available, which includes details
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about the transaction, such as which block it was included in, the actual
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fee paid, gas used, all the events that it emitted and whether it was
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successful or reverted.
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_subsection: Connecting to Ethereum @<starting-connecting>
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This very first thing needed to begin interacting with the blockchain is
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connecting to it using a [[Provider]].
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_heading: MetaMask (and other injected providers)
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The quickest and easiest way to experiment and begin developing
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on Ethereum is to use [[link-metamask]], which is a browser
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extension that injects objects into the ``window``, providing:
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- read-only access to the Ethereum network (a [[Provider]])
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- authenticated write access backed by a private key (a [[Signer]])
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When requesting access to the authenticated methods, such as
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sending a transaction or even requesting the private key address,
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MetaMask will show a pop-up to the user asking for permission.
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_code: @lang<script>
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let signer = null;
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let provider;
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if (window.ethereum == null) {
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// If MetaMask is not installed, we use the default provider,
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// which is backed by a variety of third-party services (such
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// as INFURA). They do not have private keys installed,
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// so they only have read-only access
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console.log("MetaMask not installed; using read-only defaults")
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provider = ethers.getDefaultProvider()
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} else {
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// Connect to the MetaMask EIP-1193 object. This is a standard
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// protocol that allows Ethers access to make all read-only
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// requests through MetaMask.
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provider = new ethers.BrowserProvider(window.ethereum)
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// It also provides an opportunity to request access to write
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// operations, which will be performed by the private key
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// that MetaMask manages for the user.
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signer = await provider.getSigner();
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}
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_heading: Custom RPC Backend
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If you are running your own Ethereum node (e.g. [[link-geth]])
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or using a custom third-party service (e.g. [[link-infura]]),
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you can use the [[JsonRpcProvider]] directly, which communicates
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using the [[link-jsonrpc]] protocol.
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When using your own Ethereum node or a developer-base blockchain,
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such as Hardhat or Ganache, you can get access to the accounts with
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[[JsonRpcProvider-getSigner]].
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_code: connecting to a JSON-RPC URL @lang<script>
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// If no %%url%% is provided, it connects to the default
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// http://localhost:8545, which most nodes use.
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provider = new ethers.JsonRpcProvider(url)
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// Get write access as an account by getting the signer
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signer = await provider.getSigner()
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_subsection: User Interaction @<starting-display>
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All units in Ethereum tend to be integer values, since dealing with
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decimals and floating points can lead to imprecise and non-obvious
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results when performing mathematic operations.
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As a result, the internal units used (e.g. wei) which are suited for
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machine-readable purposes and maths are often very large and not
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easily human-readable.
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For example, imagine dealing with dollars and cents; you would show
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values like ``"$2.56"``. In the blockchain world, we would keep all
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values as cents, so that would be ``256`` cents, internally.
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So, when accepting data that a user types, it must be converted from
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its decimal string representation (e.g. ``"2.56"``) to its lowest-unit
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integer representation (e.g. ``256``). And when displaying a value to
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a user the opposite operation is necessary.
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In Ethereum, //one ether// is equal to ``10 *\* 18`` wei and //one gwei//
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is equal to ``10 *\* 9`` wei, so the values get very large very quickly,
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so some convenience functions are provided to help convert between
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representations.
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_code: @lang<javascript>
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// Convert user-provided strings in ether to wei for a value
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eth = parseEther("1.0")
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//_result:
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// Convert user-provided strings in gwei to wei for max base fee
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feePerGas = parseUnits("4.5", "gwei")
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//_result:
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// Convert a value in wei to a string in ether to display in a UI
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formatEther(eth)
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//_result:
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// Convert a value in wei to a string in gwei to display in a UI
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formatUnits(feePerGas, "gwei")
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//_result:
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_subsection: Interacting with the Blockchain @<starting-blockchain>
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_heading: Querying State
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Once you have a [[Provider]], you have a read-only connection to
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the data on the blockchain. This can be used to query the current
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account state, fetch historic logs, look up contract code and so on.
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_code: @lang<javascript>
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//_hide: provider = new InfuraProvider();
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// Look up the current block number (i.e. height)
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await provider.getBlockNumber()
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//_result:
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// Get the current balance of an account (by address or ENS name)
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balance = await provider.getBalance("ethers.eth")
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//_result:
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// Since the balance is in wei, you may wish to display it
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// in ether instead.
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formatEther(balance)
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//_result:
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// Get the next nonce required to send a transaction
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await provider.getTransactionCount("ethers.eth")
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//_result:
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_heading: Sending Transactions
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To write to the blockchain you require access to a private key
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which controls some account. In most cases, those private keys
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are not accessible directly to your code, and instead you make
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requests via a [[Signer]], which dispatches the request to a
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service (such as [[link-metamask]]) which provides strictly
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gated access and requires feedback to the user to approve or
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reject operations.
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_code: @lang<script>
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//_hide: provider = new JsonRpcProvider("http:/\/localhost:8545")
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//_hide: provider.resolveName = () => "0x643aA0A61eADCC9Cc202D1915D942d35D005400C";
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//_hide: signer = new Wallet(id("test"), provider);
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// When sending a transaction, the value is in wei, so parseEther
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// converts ether to wei.
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tx = await signer.sendTransaction({
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to: "ethers.eth",
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value: parseEther("1.0")
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});
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//_result:
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// Often you may wish to wait until the transaction is mined
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receipt = await tx.wait();
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//_result:
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_subsection: Contracts @<starting-contracts>
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A **Contract** is a meta-class, which means that its definition
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its derived at run-time, based on the ABI it is passed, which then
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determined what methods and properties are available on it.
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_heading: Application Binary Interface (ABI)
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Since all operations that occur on the blockchain must be encoded
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as binary data, we need a concise way to define how to convert
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between common objects (like strings and numbers) and its binary
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representation, as well as encode the ways to call and interpret
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the Contract.
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For any method, event or error you wish to use, you must include a
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[[Fragment]] to inform Ethers how it should encode the request and
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decode the result.
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Any methods or events that are not needed can be safely excluded.
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There are several common formats available to describe an ABI. The
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Solidity compiler usually dumps a JSON representation but when typing
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an ABI by hand it is often easier (and more readable) to use the
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human-readable ABI, which is just the Solidity signature.
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_code: simplified ERC-20 ABI @lang<script>
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abi = [
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"function decimals() view returns (string)",
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"function symbol() view returns (string)",
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"function balanceOf(address addr) view returns (uint)"
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]
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// Create a contract
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contract = new Contract("dai.tokens.ethers.eth", abi, provider)
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_heading: Read-only methods (i.e. ``view`` and ``pure``)
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A read-only method is one which cannot change the state of the
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blockchain, but often provide a simple interface to get important
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data about a Contract.
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_code: reading the DAI ERC-20 contract @lang<javascript>
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// The contract ABI (fragments we care about)
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abi = [
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"function decimals() view returns (uint8)",
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"function symbol() view returns (string)",
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"function balanceOf(address a) view returns (uint)"
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]
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// Create a contract; connected to a Provider, so it may
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// only access read-only methods (like view and pure)
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contract = new Contract("dai.tokens.ethers.eth", abi, provider)
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// The symbol name for the token
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sym = await contract.symbol()
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//_result:
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// The number of decimals the token uses
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decimals = await contract.decimals()
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//_result:
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// Read the token balance for an account
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balance = await contract.balanceOf("ethers.eth")
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//_result:
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// Format the balance for humans, such as in a UI
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formatUnits(balance, decimals)
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//_result:
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_heading: State-changing Methods
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_code: change state on an ERC-20 contract @lang<script>
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abi = [
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"function transfer(address to, uint amount)"
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]
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// Connected to a Signer; can make state changing transactions,
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// which will cost the account ether
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contract = new Contract("dai.tokens.ethers.eth", abi, signer)
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// Send 1 DAI
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amount = parseUnits("1.0", 18);
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// Send the transaction
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tx = await contract.transfer("ethers.eth", amount)
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//_result: @TODO
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// Currently the transaction has been sent to the mempool,
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// but has not yet been included. So, we...
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// ...wait for the transaction to be included.
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await tx.wait()
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//_result: @TODO
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_code: forcing a call (simulation) of a state-changing method @lang<javascript>
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abi = [
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"function transfer(address to, uint amount) returns (bool)"
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]
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// Connected to a Provider since we only require read access
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contract = new Contract("dai.tokens.ethers.eth", abi, provider)
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amount = parseUnits("1.0", 18)
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// There are many limitations to using a static call, but can
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// often be useful to preflight a transaction.
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await contract.transfer.staticCall("ethers.eth", amount)
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//_result:
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// We can also simulate the transaction as another account
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other = new VoidSigner("0x643aA0A61eADCC9Cc202D1915D942d35D005400C")
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contractAsOther = contract.connect(other.connect(provider))
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await contractAsOther.transfer.staticCall("ethers.eth", amount)
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//_result:
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_heading: Listening to Events
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When adding event listeners for a named event, the event parameters
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are destructed for the listener.
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There is always one additional parameter passed to a listener, which
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is an [[EventPayload]], which includes more information about the event
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including the filter and a method to remove that listener.
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_code: listen for ERC-20 events @lang<script>
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abi = [
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"event Transfer(address indexed from, address indexed to, uint amount)"
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]
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// Create a contract; connected to a Provider, so it may
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// only access read-only methods (like view and pure)
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contract = new Contract("dai.tokens.ethers.eth", abi, provider)
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// Begin listening for any Transfer event
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contract.on("Transfer", (from, to, _amount, event) => {
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const amount = formatEther(_amount, 18)
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console.log(`${ from } => ${ to }: ${ amount }`);
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// The `event.log` has the entire EventLog
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// Optionally, stop listening
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event.removeListener();
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});
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// Same as above
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contract.on(contract.filters.Transfer, (from, to, amount, event) => {
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// See above
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})
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// Listen for any Transfer to "ethers.eth"
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filter = contract.filters.Transfer("ethers.eth")
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contract.on(filter, (from, to, amount, event) => {
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// `to` will always be equal to the address of "ethers.eth"
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});
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// Listen for any event, whether it is present in the ABI
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// or not. Since unknown events can be picked up, the
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// parameters are not destructed.
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contract.on("*", (event) => {
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// The `event.log` has the entire EventLog
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});
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_heading: Query Historic Events
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When querying within a large range of blocks, some backends may
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be prohibitively slow, may return an error or may truncate the
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results without any indication. This is at the discretion of each
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backend.
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_code: query historic ERC-20 events @lang<javascript>
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abi = [
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"event Transfer(address indexed from, address indexed to, uint amount)"
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]
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// Create a contract; connected to a Provider, so it may
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// only access read-only methods (like view and pure)
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contract = new Contract("dai.tokens.ethers.eth", abi, provider)
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// Query the last 100 blocks for any transfer
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filter = contract.filters.Transfer
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events = await contract.queryFilter(filter, -100)
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// The events are a normal Array
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events.length
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//_result:
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// The first matching event
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events[0]
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//_result:
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// Query all time for any transfer to ethers.eth
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filter = contract.filters.Transfer("ethers.eth")
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events = await contract.queryFilter(filter)
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// The first matching event
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events[0]
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//_result:
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_subsection: Signing Messages @<starting-signing>
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A private key can do a lot more than just sign a transaction to authorize
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it. It can also be used to sign other forms of data, which are then able
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to be validated for other purposes.
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For example, signing **a message** can be used to prove ownership of an
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account which a website could use to authenticate a user and log them in.
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_code: @lang<javascript>
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// Our signer; Signing messages does not require a Provider
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signer = new Wallet(id("test"))
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//_result:
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message = "sign into ethers.org?"
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// Signing the message
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sig = await signer.signMessage(message);
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//_result:
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// Validating a message; notice the address matches the signer
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verifyMessage(message, sig)
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//_result:
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_null:
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Many other more advanced protocols built on top of signed messages are
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used to allow a private key to authorize other users to transfer their
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tokens, allowing the transaction fees of the transfer to be paid by
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someone else.
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