ERC-1155 multi-token standard in Blockchain / Solidity - Mini Project: Build & Apply

ERC-1155 Multi-Token Standard Basic Contract

📖 Scenario: You are creating a simple blockchain contract to manage multiple types of tokens in one place. This is useful for games or collectibles where you want to handle many items efficiently.

🎯 Goal: Build a basic ERC-1155 contract that can hold different token types and allow minting new tokens.

📋 What You'll Learn

Create a contract named MyMultiToken that inherits from ERC1155

Set the base URI to https://token-cdn-domain/{id}.json

Create a public function mint that allows minting a specific amount of a token ID to an address

Use the _mint function from ERC1155 inside mint

Print the token URI for a given token ID

💡 Why This Matters

🌍 Real World

ERC-1155 contracts are used in blockchain games and digital collectibles to manage many token types efficiently in one contract.

💼 Career

Understanding ERC-1155 is important for blockchain developers working on NFTs, gaming, and multi-token platforms.

1

Set up the ERC-1155 contract

Write a Solidity contract named MyMultiToken that inherits from ERC1155. Set the constructor to call ERC1155 with the URI "https://token-cdn-domain/{id}.json".

Blockchain / Solidity

// Your code here

Hint

Use contract MyMultiToken is ERC1155 and call the parent constructor with the URI.

2

Add a mint function

Add a public function named mint that takes address to, uint256 id, and uint256 amount as parameters. Inside it, call _mint(to, id, amount, "").

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";

contract MyMultiToken is ERC1155 {
    constructor() ERC1155("https://token-cdn-domain/{id}.json") {
    }

    // Your code here
}

Hint

Create a mint function that calls _mint with the given parameters and empty data.

3

Add a function to get token URI

Add a public view function named getTokenURI that takes uint256 id and returns a string memory. Inside, return the result of uri(id).

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";

contract MyMultiToken is ERC1155 {
    constructor() ERC1155("https://token-cdn-domain/{id}.json") {
    }

    function mint(address to, uint256 id, uint256 amount) public {
        _mint(to, id, amount, "");
    }

    // Your code here
}

Hint

Use the inherited uri function to get the token URI for the given id.

4

Test minting and getting token URI

Write a comment showing how to call mint to mint 10 tokens of ID 1 to address 0x123.... Then write a comment showing how to call getTokenURI for token ID 1.

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";

contract MyMultiToken is ERC1155 {
    constructor() ERC1155("https://token-cdn-domain/{id}.json") {
    }

    function mint(address to, uint256 id, uint256 amount) public {
        _mint(to, id, amount, "");
    }

    function getTokenURI(uint256 id) public view returns (string memory) {
        return uri(id);
    }

    // Your code here
}

Hint

Show example calls as comments with the exact address and token ID.

Practice

1. What is the main advantage of the ERC-1155 token standard compared to ERC-20 and ERC-721?

easy

A. It only supports fungible tokens.

B. It allows managing multiple token types in a single contract.

C. It is designed exclusively for non-fungible tokens.

D. It requires a separate contract for each token type.

Solution

1. Step 1: Understand ERC-20 and ERC-721 limitations

   ERC-20 supports fungible tokens only, and ERC-721 supports non-fungible tokens but each token type needs its own contract.

2. Step 2: Identify ERC-1155 feature

   ERC-1155 allows multiple token types (fungible and non-fungible) to be managed within a single contract efficiently.

3. Final Answer:

   It allows managing multiple token types in a single contract. -> Option B

4. Quick Check:

   ERC-1155 = multi-token single contract [OK]

Hint: ERC-1155 = many tokens, one contract [OK]

Common Mistakes:

• Thinking ERC-1155 supports only one token type
• Confusing ERC-1155 with ERC-20 or ERC-721
• Believing ERC-1155 requires multiple contracts

2. Which of the following is the correct Solidity function signature to mint multiple tokens in ERC-1155?

easy

A. function mintBatch(address to, uint256[] ids, uint256[] amounts, bytes data) external;

B. function mintToken(address to, uint256 id) external;

C. function mint(address to, uint256 id, uint256 amount, bytes data) external;

D. function mintSingle(address to, uint256 id, uint256 amount) external;

Solution

1. Step 1: Recall ERC-1155 minting functions

   ERC-1155 defines mintBatch to mint multiple token types at once, taking arrays of ids and amounts.

2. Step 2: Match function signature

   function mintBatch(address to, uint256[] ids, uint256[] amounts, bytes data) external; matches the standard signature: mintBatch(address to, uint256[] ids, uint256[] amounts, bytes data).

3. Final Answer:

   function mintBatch(address to, uint256[] ids, uint256[] amounts, bytes data) external; -> Option A

4. Quick Check:

   mintBatch = batch minting function [OK]

Hint: Batch mint uses arrays of ids and amounts [OK]

Common Mistakes:

• Using single id and amount for batch mint
• Confusing mintBatch with mintSingle
• Missing bytes data parameter

3. Given the following Solidity snippet, what will be the balance of token ID 5 for address 0xABC after execution?

_mint(0xABC, 5, 10, "");
_mintBatch(0xABC, [5, 7], [5, 3], "");

medium

A. 10

B. 5

C. 15

D. 3

Solution

1. Step 1: Analyze first mint call

   The first call mints 10 tokens of ID 5 to address 0xABC.

2. Step 2: Analyze mintBatch call

   The batch mint adds 5 tokens of ID 5 and 3 tokens of ID 7 to the same address.

3. Step 3: Calculate total balance for token ID 5

   Total = 10 (first mint) + 5 (batch mint) = 15 tokens.

4. Final Answer:

   15 -> Option C

5. Quick Check:

   10 + 5 = 15 tokens [OK]

Hint: Add amounts from all mints for same token ID [OK]

Common Mistakes:

• Ignoring batch mint amounts
• Confusing token IDs in batch mint
• Assuming batch mint overwrites balance

4. Identify the error in this ERC-1155 transfer function snippet:

function safeTransferFrom(address from, address to, uint256 id, uint256 amount, bytes data) public {
    require(balanceOf(from, id) >= amount, "Insufficient balance");
    balances[from][id] -= amount;
    balances[to][id] += amount;
}

medium

A. Missing event emission after transfer.

B. Incorrect parameter types for safeTransferFrom.

C. Using 'public' instead of 'external' visibility.

D. No check if 'to' is a smart contract supporting ERC-1155.

Solution

1. Step 1: Review ERC-1155 transfer requirements

   ERC-1155 requires checking if the recipient is a contract and supports the interface to avoid tokens being locked.

2. Step 2: Identify missing safety check

   The snippet lacks the call to onERC1155Received for smart contract recipients.

3. Final Answer:

   No check if 'to' is a smart contract supporting ERC-1155. -> Option D

4. Quick Check:

   Check recipient contract support to prevent token loss [OK]

Hint: Always check recipient contract supports ERC-1155 [OK]

Common Mistakes:

• Forgetting safe transfer acceptance check
• Assuming event emission is enough
• Ignoring contract recipient handling

5. You want to create a game inventory using ERC-1155 where players can hold multiple types of items. Which approach best uses ERC-1155 features to efficiently track and transfer items?

hard

A. Deploy one ERC-1155 contract with unique IDs for each item type and use batch transfers for multiple items.

B. Deploy separate ERC-721 contracts for each item type and transfer items individually.

C. Use ERC-20 tokens for each item type and transfer amounts representing item counts.

D. Create one ERC-1155 contract but mint only one token type for all items.

Solution

1. Step 1: Understand game inventory needs

   Players hold many item types, needing efficient tracking and transfers.

2. Step 2: Evaluate ERC-1155 advantages

   ERC-1155 supports multiple token IDs in one contract and batch transfers, reducing gas and complexity.

3. Step 3: Compare options

   Deploy one ERC-1155 contract with unique IDs for each item type and use batch transfers for multiple items. uses one contract with unique IDs and batch transfers, matching ERC-1155 strengths. Others use less efficient or wrong standards.

4. Final Answer:

   Deploy one ERC-1155 contract with unique IDs for each item type and use batch transfers for multiple items. -> Option A

5. Quick Check:

   One contract + batch transfers = efficient multi-item management [OK]

Hint: Use one ERC-1155 contract with batch transfers for many items [OK]

Common Mistakes:

• Using multiple contracts unnecessarily
• Choosing ERC-20 or ERC-721 for multi-item inventory
• Minting only one token type for all items