了解以太坊中 Smart Contract 的工作原理

Source: Dev.to

Introduction

Solidity 是一种专为在以太坊区块链上编写智能合约而设计的编程语言。智能合约是自执行的程序，包含预定义的一套规则、条件和函数。部署到区块链后，只要满足特定条件，它们就会自动运行——无需中介。

智能合约运行在 Ethereum Virtual Machine (EVM) 上，这是一个去中心化的运行时环境，确保相同的代码在每个以太坊节点上以完全相同的方式执行。这些合约负责处理交易、存储数据，并根据其编写的逻辑与其他合约交互。

How Are Smart Contracts Triggered?

智能合约不会自行运行；它们只有在被交易触发时才执行。合约可以在以下情况下被触发：

• 用户发送交易。
• 另一个智能合约调用它。
• 外部应用（dApp 后端、脚本或机器人）与之交互。

在所有情况下，执行都始于向合约地址发送的交易。

Example: Triggering a Smart Contract Using MetaMask

1. User initiates a transaction in MetaMask.
2. MetaMask prepares the transaction with the following details:
   • Contract address – which smart contract to call
   • Function selector – which function to execute
   • Parameters – input values required by the function
   • Gas limit & gas price – how much the user is willing to pay for execution
   • Value (optional) – amount of ETH (or native coin) to send

Transaction Creation and Signing

• The user reviews and signs the transaction in MetaMask.
• The signed transaction is broadcast to the network.

Block Validation and Execution

• Validators (miners or validators) include the transaction in a block.
• The EVM executes the contract code as part of block validation.

What Happens Inside the EVM?

1. Locate the contract code at the specified address.
2. Execute the function logic with the provided parameters.
3. Check conditions (e.g., balances, require statements).
4. If any check fails, the transaction reverts and all state changes are discarded (gas is still consumed).

Token Standards and Protocols

Common token standards (e.g., ERC‑20, ERC‑721) define how functions like transfer, approve, and balanceOf behave, ensuring compatibility across wallets and dApps.

Summary

• Smart contracts execute only when triggered by a transaction.
• Wallets like MetaMask prepare and sign those transactions.
• Validators execute the contract code inside the EVM.
• Execution follows strict rules, consumes gas, and the result is permanently recorded on the blockchain.