ERC-1155

What is an ERC-1155?

A smart contract multi-token standard for:

-fungible tokens (ERC-20)  
-NFTs (ERC-721)

https://eips.ethereum.org/EIPS/eip-1155

ERC-721 v.s. ERC-1155

ERC-721 tokens are good at identifying one type of object.

For example, balances are based on the entire contract for all tokenId values:

Solidity

balanceOf(address)

ERC-1155 tokens are good at identifying multiple objects.

For example, balances are isolated based on unique tokenId values:

Solidity

balanceOf(address, tokenId)

Vending Machine Analogy

ERC-721:

-Example: Water Bottles
-Each tokenId represents a unique water bottle brand

ERC-1155:

-Example: Vending Machine Items
-Each tokenId can be a different vending machine item:
    -water bottles
    -snack bars
    -tea
    -trail mix

ERC-1155 Batch Transfer

You can bulk transfer ERC-1155 tokens based on tokenId and quantity by calling:

Solidity

safeBatchTransferFrom(address from, address to, uint256[] ids, uint256[] amounts, bytes data)

What do ERC-721 and ERC-1155 contracts have in common?

OpenZeppelin contracts:

ERC721Holder.sol

and

ERC1155Holder.sol

are safety inheritance contracts. A contract must inherit these contracts to accept tokens being transferred to them.

However, ERC-20 tokens do not have a safety inheritance holder contract.

When transferring tokens to contracts, call smart contract functions that have "transferFrom()" behavior. It is recommended to only send tokens directly to a contract on test networks, otherwise you risk accidentally burning your tokens.

ERC-1155 Example Contracts:

Here is how to mint and burn ERC-1155 tokens:

Solidity

// SPDX-License-Identifier: MIT
pragma solidity 0.8.17;

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "@openzeppelin/contracts/token/ERC1155/utils/ERC1155Holder.sol";

error invalidFruitIdNumber();

contract FruitStore is ERC1155 { //ERC1155 cannot also be a ERC1155Holder for having tokens ERC1155 tokens sent to it.

    uint public constant Raspberry = 0; // "constant" and "immutable" variables don't use storage slots, which saves gas.
    uint public constant Watermelon = 1; // "constant" variables can never change.
    uint public constant Blueberry = 2;
    uint public constant Avacado = 3;
    uint public constant Guava = 4;
    uint public constant Pitaya = 5;
    uint public constant Apple = 6;
    uint public constant Banana = 7;
    uint public immutable ExtraFruitId; //"immutable" can only be changed in the constructor.

    constructor(uint extraFruitIdPick) ERC1155("https://en.wikipedia.org/wiki/{name}") { //When using safeTransferFrom, have data as 0x00.
        if(extraFruitIdPick > 7) { revert invalidFruitIdNumber(); } //Don't check for negative since uint must be 0 or positive.
        ExtraFruitId = extraFruitIdPick; //"immutable" can only be changed in the constructor.
        _mint(msg.sender, Raspberry,    100*(1 ether), "");  //To send tokens from wallet to wallet, send the following Tx to this contract: "setApprovalForAll(walletToSendTo,true)".
        _mint(msg.sender, Watermelon,   100*(1 ether), "");  //Then you can transfer tokens with: "safeTransferFrom(fromAddress,toAddress,id,amount,0x00)".
        _mint(msg.sender, Blueberry,    100*(1 ether), "");  //Smart contracts must inherit "ERC1155Holder.sol" to receive ERC1155 tokens.
        _mint(msg.sender, Avacado,      100*(1 ether), "");
        _mint(msg.sender, Guava,        100*(1 ether), "");
        _mint(msg.sender, Pitaya,       100*(1 ether), "");
        _mint(msg.sender, Apple,        100*(1 ether), "");
        _mint(msg.sender, Banana,       100*(1 ether), "");
        _mint(msg.sender, ExtraFruitId, 100*(1 ether), "");
    }

}

contract BurnTokensERC1155 is ERC1155Holder {} //Tokens sent to this contract will be lost forever.