มาตรฐานโทเค็นแบบทดแทนกันได้ ERC-20

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.

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.

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.

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.

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:

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.

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.

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.

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.

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.

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!