ERC-1155 multi-token standard in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the ERC-1155 contract inheritance.

Blockchain / Solidity

contract MyToken is [1] {
    // contract code
}

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AERC20

BERC1155

CERC721

DOwnable

Attempts:

3 left

💡 Hint

Common Mistakes

Using ERC20 or ERC721 inheritance instead of ERC1155.

Forgetting to inherit any contract.

The ERC-1155 standard contract inherits from ERC1155 in Solidity.

2fill in blank

medium

Complete the code to mint a new token with a specific ID and amount.

Blockchain / Solidity

function mintToken(address to, uint256 id, uint256 amount) public {
    _mint(to, id, [1], "");
}

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Aid

Bmsg.sender

Camount

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the recipient address instead of amount.

Passing the token ID instead of amount.

The _mint function requires the amount of tokens to mint as the third argument.

3fill in blank

hard

Fix the error in the transfer function call by completing the missing argument.

Blockchain / Solidity

safeTransferFrom(msg.sender, to, id, amount, [1]);

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A""

Baddress(0)

C0x0

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using null or zero address instead of empty bytes.

Omitting the last parameter.

The last argument is a bytes data parameter, usually an empty string "" when no data is sent.

4fill in blank

hard

Fill both blanks to create a mapping for balances of token IDs per address.

Blockchain / Solidity

mapping(address => mapping(uint256 => [1])) private [2];

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Auint256

Baddress

Cbalances

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using address or bool as the value type.

Incorrect variable name.

The balances mapping stores the amount (uint256) of each token ID per address.

5fill in blank

hard

Fill all three blanks to implement a function that returns the URI for a given token ID.

Blockchain / Solidity

function uri(uint256 [1]) public view override returns (string memory) {
    return string(abi.encodePacked([2], Strings.[3]([1]), ".json"));
}

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AtokenId

BbaseURI

CtoString

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names.

Forgetting to convert the token ID to string.

The function takes tokenId, concatenates baseURI with the string version of tokenId using toString, and adds the .json extension.

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