In this tutorial, we will guide you step-by-step in creating royalty NFTs using ERC-2981.ERC-2981, also known as the NFT Royalty Standard, proposes a new Ethereum token standard that enables creators to receive a percentage of each subsequent sale of their NFTs on the secondary market. It defines rules for calculating and automatically transferring royalty payments to the creator's wallet whenever their NFT is resold on the secondary market.To get you started quickly, we have already set everything up for you. Let's begin by making a copy of the repository.<h1>Step 1: Cloning the Tutorial Repo</h1>1.1 Forking the Tutorial Repository:<ul><li>Visit our&nbsp;<a href="https://github.com/BuildBearLabs/Tutorials">Tutorial Repository</a>&nbsp;and click the "Fork" button to duplicate the repository into your own account. Please wait until the forking process is complete before proceeding.</li></ul>1.2 Cloning the repository locally:<ul><li>Go to your forked repository on GitHub.</li><li>Click the "Code" button and copy the URL provided (either HTTPS or SSH).</li><li>Open your terminal or Git Bash.</li><li>Navigate to the directory where you want to place the cloned repository.</li><li>Use the following command to clone the repository:</li></ul><pre><code class="language-plaintext">git clone &lt;paste the copied URL here&gt;
</code></pre><ul><li>Wait for the cloning process to finish. Once completed, you should see a new directory with the repository's name in the chosen directory.</li><li>To access the cloned repository, use the command&nbsp;<code>cd &lt;Name of the cloned Repo&gt;</code>, and then navigate to the ERC-6551 folder by executing&nbsp;<code>cd ERC-2981</code>.</li></ul>Step 2: Developing the smart contract2.1 <code>RoyaltyNFT</code> Smart Contract<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/carbon_32_2ee22d5153.png" alt="carbon_(32).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_carbon_32_2ee22d5153.png 245w,https://strapi.buildbear.io/uploads/small_carbon_32_2ee22d5153.png 500w,https://strapi.buildbear.io/uploads/medium_carbon_32_2ee22d5153.png 750w,https://strapi.buildbear.io/uploads/large_carbon_32_2ee22d5153.png 1000w," sizes="100vw"></figure>Let's break it down:The contract imports three different contracts from the OpenZeppelin library:<ul><li><code>ERC721Royalty.sol</code>: This contract implements ERC-2981, which introduces royalty functionality for ERC-721 tokens. It allows NFT creators to receive a fee whenever their NFT is resold in a secondary market.</li><li><code>Ownable.sol</code>: This contract provides basic access control, allowing certain functions to be restricted to the contract's owner.</li><li><code>Counters.sol</code>: This contract helps to manage and generate unique token IDs for the NFTs.</li></ul>constructor(address _receiver, uint96 feeNumerator): This is the constructor function that is executed once when the contract is deployed. It takes two parameters: <code>_receiver</code> (the default royalty receiver) and <code>feeNumerator</code> (the default royalty fee numerator).Inside the constructor, the <code>ERC721</code> constructor is called with the token name "Royalties" and symbol "RYLT" to initialize the ERC-721 metadata.Additionally, the <code>_setDefaultRoyalty</code> function from <code>ERC721Royalty</code> is called to set the default royalty receiver and fee numerator for all NFTs minted using this contract.function safeMint(address to) public onlyOwner: This function allows the contract owner to mint a new NFT and assign it to the specified address <code>to</code>. It increments the <code>_tokenIdCounter</code> to generate a unique token ID for the newly minted NFT. The <code>onlyOwner</code> modifier ensures that only the contract owner can call this function.function setTokenRoyalty(uint256 tokenId, address receiver, uint96 feeNumerator) public onlyOwner: This function allows the contract owner to set the royalty for a specific token (<code>tokenId</code>). It takes three parameters: the <code>tokenId</code>, the new <code>receiver</code> address (the address that will receive royalties when the token is sold), and the <code>feeNumerator</code> representing the royalty fee in parts per million (ppm). The <code>onlyOwner</code> modifier ensures that only the contract owner can call this function.In summary, the <code>RoyaltyNFT</code> contract extends ERC-721 royalty functionality using the <code>ERC721Royalty</code> contract and provides a mechanism for minting NFTs with royalty support. The contract owner can mint NFTs and set the royalty receiver and fee for each NFT. The NFT creator will receive a royalty fee whenever the NFT is sold in secondary markets.2.2 ERC2981 OpenZeppelin Smart Contract<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/carbon_34_f7044f54bf.png" alt="carbon_(34).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_carbon_34_f7044f54bf.png 134w,https://strapi.buildbear.io/uploads/small_carbon_34_f7044f54bf.png 431w,https://strapi.buildbear.io/uploads/medium_carbon_34_f7044f54bf.png 646w,https://strapi.buildbear.io/uploads/large_carbon_34_f7044f54bf.png 861w," sizes="100vw"></figure>Let's break down the contract step by step:The contract imports two other contracts/interfaces:<ul><li><code>IERC2981.sol</code>: This is the interface for the ERC-2981 standard, which defines the functions required for retrieving royalty information for NFTs.</li><li><code>ERC165.sol</code>: This is an implementation of the ERC-165 standard, which is used to support multiple interfaces in a single contract.</li></ul><code>ERC2981</code> abstract contract: This is an abstract contract that inherits the <code>IERC2981</code> interface and the <code>ERC165</code> contract. The abstract contract provides the core functionality to manage and retrieve royalty information for NFTs.<code>struct RoyaltyInfo</code>: This struct defines the royalty information for an NFT, including the address of the royalty receiver and the royalty fraction represented as a <code>uint96</code> (a fraction out of 10000).Private state variables:<ul><li><code>_defaultRoyaltyInfo</code>: This variable holds the default royalty information for all token IDs that do not have individual royalty information set. It is of type <code>RoyaltyInfo</code>.</li><li><code>_tokenRoyaltyInfo</code>: This mapping stores individual royalty information for specific token IDs. It maps a token ID (<code>uint256</code>) to a <code>RoyaltyInfo</code> struct.</li></ul>Function <code>supportsInterface</code>: This function overrides the <code>supportsInterface</code> function from the <code>ERC165</code> contract. It checks if the contract supports the ERC-2981 interface or any other supported interface.Function <code>royaltyInfo</code>: This function implements the <code>royaltyInfo</code> function from the <code>IERC2981</code> interface. It retrieves the royalty information for a given token ID and sale price. If the token ID has specific royalty information set using <code>_setTokenRoyalty</code>, that information is used. Otherwise, the function falls back to the default royalty information set using <code>_setDefaultRoyalty</code>. It calculates the royalty amount based on the sale price and the royalty fraction.Function <code>_feeDenominator</code>: This internal pure function defines the denominator used to interpret the royalty fee set in <code>_setTokenRoyalty</code> and <code>_setDefaultRoyalty</code>. By default, it returns <code>10000</code>, meaning the fee is specified in basis points (1% = 100 basis points). It can be customized by overriding it in derived contracts.Internal functions:<ul><li><code>_setDefaultRoyalty</code>: This internal function sets the default royalty information for all token IDs in the contract. It takes the receiver address and the fee numerator (royalty fraction) as parameters and saves them in the <code>_defaultRoyaltyInfo</code> variable. It ensures that the fee numerator is not greater than the fee denominator (10000) and that the receiver address is valid.</li><li><code>_deleteDefaultRoyalty</code>: This internal function deletes the default royalty information, effectively removing the default royalty for all token IDs.</li><li><code>_setTokenRoyalty</code>: This internal function sets the royalty information for a specific token ID, overriding the global default. It takes the token ID, receiver address, and fee numerator as parameters and saves them in the <code>_tokenRoyaltyInfo</code> mapping. It ensures that the fee numerator is not greater than the fee denominator (10000) and that the receiver address is valid.</li><li><code>_resetTokenRoyalty</code>: This internal function resets the royalty information for a specific token ID back to the global default by deleting the entry from the <code>_tokenRoyaltyInfo</code> mapping.</li></ul>Step 3: Setting up the Infrastructure for Deploying and Testing the Smart Contract3.1. Visit the&nbsp;<a href="https://buildbear.io/">BuildBear App</a>. (Wondering why BuildBear? Check out the article&nbsp;<a href="https://medium.com/@thomas_90087/a-thank-you-to-buildbear-5873b8394da5">here</a>).3.2. Create your Private Testnet. You have the option to either fork from the Mainnets or create a new Testnet from scratch, using Mainnet as the base.&nbsp;<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/image_11_f2acd5ddd3.png" alt="image (11).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_image_11_f2acd5ddd3.png 245w,https://strapi.buildbear.io/uploads/small_image_11_f2acd5ddd3.png 500w,https://strapi.buildbear.io/uploads/medium_image_11_f2acd5ddd3.png 750w,https://strapi.buildbear.io/uploads/large_image_11_f2acd5ddd3.png 1000w," sizes="100vw"></figure>3.3. Add your Private Testnet to your MetaMask wallet by using the “Add to Metamask” button:<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/image_12_9b694c7d22.png" alt="image (12).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_image_12_9b694c7d22.png 245w,https://strapi.buildbear.io/uploads/small_image_12_9b694c7d22.png 500w,https://strapi.buildbear.io/uploads/medium_image_12_9b694c7d22.png 750w,https://strapi.buildbear.io/uploads/large_image_12_9b694c7d22.png 1000w," sizes="100vw"></figure>Step 4: Deploying the Smart ContractTo begin, execute the following command to install the necessary packages:<pre><code class="language-plaintext">npm install
</code></pre>4.1 Update the&nbsp;<code>hardhat.config.js</code>&nbsp;file:<ul><li>Go to your Dashboard and click on "verify contract".</li></ul><figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/image_13_8005f0ace7.png" alt="image (13).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_image_13_8005f0ace7.png 245w,https://strapi.buildbear.io/uploads/small_image_13_8005f0ace7.png 500w,https://strapi.buildbear.io/uploads/medium_image_13_8005f0ace7.png 750w,https://strapi.buildbear.io/uploads/large_image_13_8005f0ace7.png 1000w," sizes="100vw"></figure><figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/image_14_45aa356776.png" alt="image (14).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_image_14_45aa356776.png 185w,https://strapi.buildbear.io/uploads/small_image_14_45aa356776.png 500w,https://strapi.buildbear.io/uploads/medium_image_14_45aa356776.png 750w,https://strapi.buildbear.io/uploads/large_image_14_45aa356776.png 1000w," sizes="100vw"></figure><ul><li>Copy the BuildBear and Etherscan objects, and update the&nbsp;<code>hardhat.config.js</code>&nbsp;file with the new values.</li></ul>4.2 To deploy the&nbsp;<code>RoyaltyNFT.sol</code>&nbsp;&nbsp;smart contracts, run the following command:&nbsp;<code>npx hardhat deploy</code>. This will execute the deployment scripts located in the&nbsp;<code>deploy</code>&nbsp;folder and save the deployment details, including the ABI and Contract address, in the&nbsp;<code>deployments</code>&nbsp;folder.<figure class="image image_resized" style="width:75%;"><img src="https://strapi.buildbear.io/uploads/Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_e2b3c2bb80.png" alt="RoyaltyNFT-test-js-Tutorials-Codespaces-Visual-Studio-Code.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_e2b3c2bb80.png 245w,https://strapi.buildbear.io/uploads/small_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_e2b3c2bb80.png 500w,https://strapi.buildbear.io/uploads/medium_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_e2b3c2bb80.png 750w,https://strapi.buildbear.io/uploads/large_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_e2b3c2bb80.png 1000w," sizes="100vw"></figure>Click on the explorer link provided in the terminal, as shown below you can see that the contract is verified<figure class="image image_resized" style="width:75%;"><img src="https://strapi.buildbear.io/uploads/Untitled_edc1f1a398.png" alt="Untitled.png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Untitled_edc1f1a398.png 222w,https://strapi.buildbear.io/uploads/small_Untitled_edc1f1a398.png 500w,https://strapi.buildbear.io/uploads/medium_Untitled_edc1f1a398.png 750w,https://strapi.buildbear.io/uploads/large_Untitled_edc1f1a398.png 1000w," sizes="100vw"></figure>Testing RoyaltyNFT.sol smart contract using RoyaltyNFT.test.js test scripts.<figure class="image image_resized" style="width:75%;"><img src="https://strapi.buildbear.io/uploads/carbon_35_d11071d781.png" alt="carbon_(35).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_carbon_35_d11071d781.png 134w,https://strapi.buildbear.io/uploads/small_carbon_35_d11071d781.png 431w,https://strapi.buildbear.io/uploads/medium_carbon_35_d11071d781.png 646w,https://strapi.buildbear.io/uploads/large_carbon_35_d11071d781.png 861w," sizes="100vw"></figure>These test scripts are testing various functionalities of the <code>RoyaltyNFT</code> contract related to minting NFTs and setting royalty information. The test cases are written using Hardhat and Chai testing libraries. Let's go through each test case one by one:<ol><li><code>it("Should mint an NFT and set default royalty", async function () { ... })</code>:<ul><li>The test is checking that after minting an NFT, the default royalty receiver should be the contract creator (<code>addr1.address</code>), and the default royalty fee numerator should be equal to 1 ether (<code>ethers.utils.parseUnits("1", "ether")</code>).</li></ul></li><li><code>it("Should update default token royalty", async function () { ... })</code>:<ul><li>The test is checking that after minting an NFT and updating the default royalty, the new royalty receiver should be <code>addr2.address</code>, and the new royalty fee numerator should be equal to 0.5 ether (<code>ethers.utils.parseUnits("0.5", "ether")</code>), representing 50% royalty fee.</li></ul></li><li><code>it("Should not allow setting token royalty by non-owner", async function () { ... })</code>:<ul><li>The test is checking that when a non-owner (<code>addr2</code>) tries to set the royalty information for an NFT, the transaction should revert with the error message "Ownable: caller is not the owner," indicating that setting token royalty is only allowed for the contract owner (<code>owner.address</code>).</li></ul></li></ol>To run the <code>RoyaltyNFT.test.js</code> test scripts, run the following command:&nbsp;<code>npx hardhat test</code>.<figure class="image image_resized" style="width:50%;"><img src="https://strapi.buildbear.io/uploads/Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_1_758cfd6bd3.png" alt="RoyaltyNFT-test-js-Tutorials-Codespaces-Visual-Studio-Code_(1).png" srcset="https://strapi.buildbear.io/uploads/thumbnail_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_1_758cfd6bd3.png 245w,https://strapi.buildbear.io/uploads/small_Royalty_NFT_test_js_Tutorials_Codespaces_Visual_Studio_Code_1_758cfd6bd3.png 500w," sizes="100vw"></figure>🎉🎉&nbsp;Congratulations!We have successfully created and tested RoyaltyNFT using OpenZeppelin ERC721Royalty extensionIf you appreciate what we are doing, please follow us on&nbsp;<a href="https://twitter.com/_BuildBear">Twitter</a>, and&nbsp;<a href="https://www.linkedin.com/company/build-bear/">LinkedIn</a>&nbsp;and&nbsp;<a href="https://t.me/+6mjOnBFUR9xjN2U1">Join the Telegram</a>&nbsp;group if you haven’t done yet.Github Repo :&nbsp; <a href="https://github.com/BuildBearLabs/Tutorials">BuildBearLabs/Tutorials</a>About BuildBear:BuildBear is a platform for testing dApps at scale, for teams. It provides users with their own private Testnet to test their smart contracts and dApps, which can be forked from any EVM chain. It also provides a Faucet, Explorer, and RPC for testing purposes.<blockquote>BuildBear aims to build an ecosystem of tools for testing dApps at scale for the teams.</blockquote>

Creating Royalty NFTs using ERC-2981: A Step-by-Step Guide

Let’s get started then, Shall we?

Let’s get started then, Shall we?

Test DApps at Scale.