Blockchain Smart Contracts with Solidity · 课时

使用 Revert/Require 处理错误

使用 `require()`、`revert()` 和 `assert()` 实施有效的错误处理策略，确保合约稳健执行。

使用 Revert/Require 处理错误 是 CoddyKit 上的免费 Blockchain Smart Contracts with Solidity 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 Blockchain Smart Contracts with Solidity 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Blockchain Smart Contracts with Solidity 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。

Robust Contracts: Error Handling

Welcome to error handling in Solidity! Writing smart contracts requires extreme care, as they often manage valuable assets and are immutable once deployed.

Effective error handling is crucial for creating robust and secure decentralized applications (dApps). It helps prevent unexpected behavior and protects users.

`require()`: Validating Inputs

The require() function is your primary tool for validating conditions that must be true before a function executes.

It checks pre-conditions and user inputs.
If the condition is false, it reverts all state changes made in the current transaction.
It refunds any remaining gas to the caller, effectively canceling the transaction.

Use require() for external conditions and user-provided data checks.

`require()` in Action

Let's see require() in a simple contract. This function only allows users older than 18 to register.

pragma solidity ^0.8.0;

contract UserRegistration {
    uint public minAge = 18;
    address[] public registeredUsers;

    function registerUser(uint _age) public {
        // Validate user input: age must be at least minAge
        require(_age >= minAge, "Must be 18 or older to register.");
        registeredUsers.push(msg.sender);
    }
}

`revert()`: Flexible Error Handling

The revert() statement offers more flexibility than require(), especially when you need to handle complex error logic or integrate with custom error types.

Like require(), it reverts all state changes and refunds gas.
It's often used inside if statements for more intricate conditional checks.
It can be called directly or with a string message, similar to require().

Custom Errors with `revert()`

Solidity 0.8.4+ introduced Custom Errors. These are more gas-efficient than string messages and provide better clarity for off-chain applications.

You define custom errors at the contract or file level, then use them with revert(). They help reduce transaction costs and improve contract readability.

Custom Error Demo

Here's how to define and use a custom error with revert(). Notice the error keyword.

pragma solidity ^0.8.4;

contract Wallet {
    address public owner;
    uint public balance;

    // Define a custom error
    error InsufficientFunds(uint requested, uint available);

    constructor() {
        owner = msg.sender;
    }

    function deposit() public payable {
        balance += msg.value;
    }

    function withdraw(uint _amount) public {
        require(msg.sender == owner, "Only owner can withdraw.");

        // Use revert() with the custom error
        if (_amount > balance) {
            revert InsufficientFunds(_amount, balance);
        }
        balance -= _amount;
        payable(owner).transfer(_amount);
    }
}

`assert()`: Internal Invariants

The assert() function is used for a very specific purpose: checking internal invariants.

It verifies conditions that should never be false if your code is working correctly.
If an assert() fails, it indicates a bug in your contract logic.
Crucially, a failed assert() consumes all remaining gas, unlike require() and revert() which refund gas.

Use assert() for post-conditions or internal consistency checks, not for user input validation.

When to Use Which?

Choosing the right error handler is key:

require(): For validating user inputs, external conditions, or state changes before execution. Refunds gas.
revert(): For more complex error logic, often with custom errors. Also refunds gas.
assert(): For internal consistency checks and invariants. Indicates a bug if it fails and consumes all gas.

Prioritize require() and revert() for expected errors, and reserve assert() for unexpected, internal errors.

Error Handling Check

You're building a function that transfers tokens. Before sending, you need to ensure the sender has enough balance. If not, the transaction should fail and refund any unused gas.

Recap: Error Handling

You've learned how to make your Solidity contracts robust with proper error handling:

require() is for validating external conditions and user inputs.
revert() offers flexibility, often used with gas-efficient custom errors.
assert() is for internal invariants, signaling a bug if it fails.

Mastering these ensures your smart contracts are secure and predictable. Great job!

常见问题解答

「使用 Revert/Require 处理错误」课时是免费的吗？

是的 — 「使用 Revert/Require 处理错误」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 Blockchain Smart Contracts with Solidity 课程的其余内容，请升级到 CoddyKit PRO。 Blockchain Smart Contracts with Solidity 课程共包含 4 节课。

「使用 Revert/Require 处理错误」这节课中我会学到什么？

使用 `require()`、`revert()` 和 `assert()` 实施有效的错误处理策略，确保合约稳健执行。你通过在浏览器中直接运行的动手代码来练习 Blockchain Smart Contracts with Solidity，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Blockchain Smart Contracts with Solidity 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Blockchain Smart Contracts with Solidity 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。

「使用 Revert/Require 处理错误」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 Blockchain Smart Contracts with Solidity 课中编写并运行代码吗？

能。每节 Blockchain Smart Contracts with Solidity 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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