Web3 & DApp Development Fundamentals · 课时

发送交易

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发送交易 是 CoddyKit 上的免费 Web3 & DApp Development Fundamentals 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Web3 & DApp Development Fundamentals 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Web3 & DApp Development Fundamentals 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Writing to the Chain

Changing contract state — transferring tokens, minting, voting — requires a transaction. Transactions must be signed and cost gas.

For this you need a signer, not just a provider.

A Contract with a Signer

To send transactions, create the contract with a signer or connect an existing instance to one:

const contract = new ethers.Contract(
  address,
  abi,
  signer
);
// or
const writable = readOnly.connect(signer);

Now state-changing functions become available.

const contract = new ethers.Contract(
  address,
  abi,
  signer
);
// or
const writable = readOnly.connect(signer);

Sending a Transaction

Calling a write function sends a transaction and returns a transaction response immediately — before it is mined:

const tx = await contract.transfer(
  recipient,
  ethers.parseUnits("10", 18)
);
console.log("Sent:", tx.hash);

The hash identifies the pending transaction.

const tx = await contract.transfer(
  recipient,
  ethers.parseUnits("10", 18)
);
console.log("Sent:", tx.hash);

Waiting for Confirmation

The transaction is not final until it is mined. Wait for the receipt:

const receipt = await tx.wait();
console.log("Mined in block:", receipt.blockNumber);
console.log("Status:", receipt.status);

A status of 1 means success; 0 means it reverted.

const receipt = await tx.wait();
console.log("Mined in block:", receipt.blockNumber);
console.log("Status:", receipt.status);

Waiting for More Blocks

For higher confidence against reorgs, wait for several confirmations:

// Wait for 3 confirmations
const receipt = await tx.wait(3);

More confirmations mean it is increasingly unlikely the transaction will be reversed.

// Wait for 3 confirmations
const receipt = await tx.wait(3);

Sending ETH with a Call

Payable functions accept ETH. Pass a value override as the last argument:

const tx = await contract.deposit({
  value: ethers.parseEther("0.5"),
});
await tx.wait();

The value is in wei; parseEther converts from a human amount.

const tx = await contract.deposit({
  value: ethers.parseEther("0.5"),
});
await tx.wait();

Estimating Gas

Before sending, you can estimate how much gas a call will use:

const gas = await contract.transfer
  .estimateGas(recipient, amount);
console.log("Estimated gas:", gas);

If the function would revert, estimation throws — a useful early warning.

const gas = await contract.transfer
  .estimateGas(recipient, amount);
console.log("Estimated gas:", gas);

Setting Gas Overrides

You can override gas parameters when needed, for example on EIP-1559 chains:

const tx = await contract.transfer(recipient, amount, {
  gasLimit: 100000,
  maxFeePerGas: ethers.parseUnits("30", "gwei"),
  maxPriorityFeePerGas: ethers.parseUnits("2", "gwei"),
});

Usually the wallet picks sensible defaults, so override only when you must.

const tx = await contract.transfer(recipient, amount, {
  gasLimit: 100000,
  maxFeePerGas: ethers.parseUnits("30", "gwei"),
  maxPriorityFeePerGas: ethers.parseUnits("2", "gwei"),
});

Handling Failures

Transactions can fail by reverting, being underpriced, or by user rejection in a wallet. Wrap sends in try/catch:

try {
  const tx = await contract.transfer(to, amount);
  await tx.wait();
} catch (err) {
  console.error("Transaction failed:", err.shortMessage);
}

try {
  const tx = await contract.transfer(to, amount);
  await tx.wait();
} catch (err) {
  console.error("Transaction failed:", err.shortMessage);
}

Nonces and Ordering

Each account has a nonce — a counter ensuring transactions execute in order. ethers manages it automatically, but if you send many transactions quickly you may set it manually to avoid collisions:

const tx = await contract.mint({ nonce: 42 });

Mismatched nonces cause transactions to get stuck or replaced.

const tx = await contract.mint({ nonce: 42 });

Reading Events from a Receipt

After mining, you can inspect the events emitted by your transaction from the receipt logs:

const receipt = await tx.wait();
for (const log of receipt.logs) {
  const parsed = contract.interface.parseLog(log);
  if (parsed) console.log(parsed.name, parsed.args);
}

This confirms the contract did what you expected.

const receipt = await tx.wait();
for (const log of receipt.logs) {
  const parsed = contract.interface.parseLog(log);
  if (parsed) console.log(parsed.name, parsed.args);
}

Quick Check

Test your understanding of sending transactions.

在交互式课程中回答

Recap

You learned to send state-changing transactions.

Writes require a signer; attach one with connect or at construction.
A write call returns a pending tx; tx.wait() gives the mined receipt.
Check receipt.status; wait for more confirmations against reorgs.
Send ETH via a value override; estimate cost with estimateGas.
Handle failures with try/catch and mind the account nonce.

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常见问题解答

「发送交易」课时是免费的吗？

是的 — 「发送交易」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Web3 & DApp Development Fundamentals 课程的其余内容，请升级到 CoddyKit PRO。 Web3 & DApp Development Fundamentals 课程共包含 4 节课。

「发送交易」这节课中我会学到什么？

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学习 Web3 & DApp Development Fundamentals 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Web3 & DApp Development Fundamentals 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「发送交易」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Web3 & DApp Development Fundamentals 课中编写并运行代码吗？

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