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Blockchain Smart Contracts with Solidity · درس

معيار الرموز القابلة للاستبدال ERC-20

تعرّف إلى مواصفات معيار ERC-20 ووظائفه لإنشاء رموز قابلة للاستبدال.

معيار الرموز القابلة للاستبدال ERC-20 درس مجاني في Blockchain Smart Contracts with Solidity على CoddyKit. هذا هو الدرس 1 من أصل 4. يمكنك قراءة الدرس كاملاً أدناه مجاناً — ثم تمرن عليه مباشرة في المتصفح باستخدام محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7. هذا الدرس جزء من مسار التعلم في Blockchain Smart Contracts with Solidity، وتقدمك يتزامن عبر الويب وتطبيق CoddyKit. تتضمن دورة Blockchain Smart Contracts with Solidity 4 دروس في المجموع.

بعض أجزاء هذا الدرس لم تُترجم بعد وتظهر باللغة الإنجليزية.

Intro to Blockchain Tokens

Welcome to the world of blockchain tokens! Beyond cryptocurrencies like Ether, blockchains host many other digital assets.

These assets, often called 'tokens', can represent anything from digital currency to ownership of real-world items, or even voting rights in a decentralized organization.

Fungibility: Interchangeable Assets

A key concept for tokens is fungibility. What does it mean?

  • Fungible: Each unit is identical and interchangeable with another. Like a dollar bill – one $1 bill is the same as any other $1 bill.
  • Non-Fungible: Each unit is unique and cannot be replaced by another. Like a piece of art or a specific house.

ERC-20 tokens are fungible, meaning every token is equal to every other token of the same type.

Meet the ERC-20 Standard

ERC-20 (Ethereum Request for Comment 20) is a technical standard for fungible tokens on the Ethereum blockchain.

It defines a common set of rules that all compliant tokens must follow. This ensures they can interact seamlessly with wallets, exchanges, and other smart contracts.

Interoperability Through Standards

Why is a standard so important?

  • Compatibility: Any wallet that supports ERC-20 can manage any ERC-20 token.
  • Ecosystem Growth: Decentralized applications (dApps) can easily integrate different tokens.
  • Predictable Behavior: Developers know exactly how an ERC-20 token will behave, making integration safer and faster.

Core Function: `totalSupply()`

The totalSupply() function returns the total number of tokens in existence. It's a public view function, meaning it doesn't change the blockchain state and costs no gas to call.

Try running this simple contract to see how totalSupply might be represented:

pragma solidity ^0.8.0;

contract SimpleTokenInfo {
    uint256 public totalTokens = 1000; // Example supply

    function totalSupply() public view returns (uint256) {
        return totalTokens;
    }
}

Core Function: `balanceOf()`

The balanceOf(address account) function returns the token balance of a specific address. It helps you check how many tokens a user owns.

Let's add balanceOf to our example. The deployer will start with all tokens.

pragma solidity ^0.8.0;

contract SimpleTokenInfo {
    uint256 public totalTokens = 1000;
    mapping(address => uint256) public balances;

    constructor() {
        balances[msg.sender] = totalTokens; // Assign all to deployer
    }

    function totalSupply() public view returns (uint256) {
        return totalTokens;
    }

    function balanceOf(address account) public view returns (uint256) {
        return balances[account];
    }
}

Core Function: `transfer()`

The transfer(address recipient, uint256 amount) function allows the sender of the transaction to send tokens directly to another address.

This is the most common way to move tokens between users.

pragma solidity ^0.8.0;

contract SimpleTokenInfo {
    uint256 public totalTokens = 1000;
    mapping(address => uint256) public balances;

    constructor() {
        balances[msg.sender] = totalTokens;
    }

    function totalSupply() public view returns (uint256) {
        return totalTokens;
    }

    function balanceOf(address account) public view returns (uint256) {
        return balances[account];
    }

    function transfer(address recipient, uint256 amount) public returns (bool) {
        require(balances[msg.sender] >= amount, "Insufficient balance");
        balances[msg.sender] -= amount;
        balances[recipient] += amount;
        return true;
    }
}

Delegated Transfers: `approve()` & `allowance()`

ERC-20 also supports delegated transfers, where one user (the owner) allows another address (the spender) to move tokens on their behalf.

  • approve(address spender, uint256 amount): The owner grants permission to a spender to withdraw a specific amount of tokens.
  • allowance(address owner, address spender): Returns the amount of tokens that the spender is currently allowed to withdraw from the owner.

Executing Delegated Transfers: `transferFrom()`

Once an approve() call has been made, the designated spender can then use the transferFrom() function.

transferFrom(address sender, address recipient, uint256 amount): Allows a spender to transfer amount tokens from the sender's balance to the recipient, provided the spender has enough allowance from the sender.

Tracking Actions: ERC-20 Events

ERC-20 defines two standard events: Transfer and Approval. These events are crucial for off-chain applications (like wallets or block explorers) to track token movements and approvals without having to read the entire blockchain state.

They emit logs that can be efficiently indexed and queried.

pragma solidity ^0.8.0;

contract EventExample {
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    function demonstrateTransferEvent(address _to, uint256 _value) public {
        // Imagine actual transfer logic here
        emit Transfer(msg.sender, _to, _value);
    }

    function demonstrateApprovalEvent(address _spender, uint256 _value) public {
        // Imagine actual approval logic here
        emit Approval(msg.sender, _spender, _value);
    }
}

Check Your Understanding

The ERC-20 standard outlines specific functions that all compliant tokens must implement. Understanding these is crucial for working with tokens.

ERC-20: Your Token Blueprint

You've now learned about the ERC-20 Fungible Token Standard! It's the blueprint for most interchangeable tokens on Ethereum.

  • It defines core functions like totalSupply(), balanceOf(), and transfer().
  • It enables delegated transfers with approve(), allowance(), and transferFrom().
  • Standard events Transfer and Approval help track token activity.

This standard ensures that all ERC-20 tokens are compatible, making the Ethereum ecosystem robust and easy to navigate. Next, we'll dive into implementing your own ERC-20 token!

الأسئلة الشائعة

هل درس «معيار الرموز القابلة للاستبدال ERC-20» مجاني؟

نعم — نص درس «معيار الرموز القابلة للاستبدال ERC-20» كامل متاح مجاناً هنا على الويب. لتمرينه بشكل تفاعلي (محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7) وفتح باقي دورة Blockchain Smart Contracts with Solidity، انتقل إلى CoddyKit PRO. تتضمن دورة Blockchain Smart Contracts with Solidity 4 دروس في المجموع.

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تعرّف إلى مواصفات معيار ERC-20 ووظائفه لإنشاء رموز قابلة للاستبدال. تتمرن على Blockchain Smart Contracts with Solidity مع أكواد عملية تشغلها مباشرة في المتصفح، ومدرس ذكاء اصطناعي متاح 24/7 يجيب على أسئلتك أثناء عملك.

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معظم دروس CoddyKit تستغرق حوالي 5–10 دقائق. كل منها موجز وتفاعلي، لذا تحرز تقدماً مستمراً وتستأنف من حيث توقفت عبر الويب والتطبيق.

هل يمكنني كتابة وتشغيل أكواد في درس Blockchain Smart Contracts with Solidity هذا؟

نعم. كل درس في Blockchain Smart Contracts with Solidity يتضمن محرر أكواد مدمج، لذا تكتب وتشغل أكواداً حقيقية مباشرة في متصفحك وتحصل على تعليقات فورية من الذكاء الاصطناعي — بدون إعداد محلي.

جميع الدروس في هذه الدورة

  1. معيار الرموز القابلة للاستبدال ERC-20
  2. تنفيذ رمز ERC-20
  3. الرموز غير القابلة للاستبدال ERC-721 (NFTs)
  4. معيار ERC-1155 للرموز المتعددة
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