Welcome degens, this is the start of a new series of blog posts about Solana development and in this one you’ll learn how to write a custom contract to mint your NFT in only 4 steps. ### Some general tips about Solana development In Solana development you’ll face a lot of weird custom errors and bugs and it can be quite hard and frustrating to fix them since the Solana dev ecosystem is not as big as the Eth dev ecosystem but not to worry degens, when you get stuck you simply have to look in the right place for the solution. During my development I was constantly asking my doubts in the [Anchor](https://discord.gg/Srq5GY3Zhe) discord server and the [Metaplex](https://discord.gg/zTRnQR3Jqm) and [Superteam](https://discord.gg/RvuYj55Ehj) server and looking through other code repos on GitHub and the Metaplex Program library itself. > **Big thanks to** [Pratik Saria](https://twitter.com/PratikSaria) **and** [0xDeep](https://twitter.com/0xDeep) **for helping me understand on how Solana NFTs and Anchor works, if it weren’t for them i’d still be trying to figure it out** ### Project Overview The tools we’ll be using for this: * [Solana CLI Tools](https://docs.solana.com/cli/install-solana-cli-tools) - The official Solana CLI toolset * [Anchor Framework](https://project-serum.github.io/anchor/getting-started/introduction.html) - A high level framework for developing Solana Programs, a must unless your a god level dev in which case your not reading this blog lol. * [Solana/web3.js](https://solana-labs.github.io/solana-web3.js/) - A Solana version of [web3.js](https://web3js.readthedocs.io/) * [Solana/spl-token](https://www.npmjs.com/package/@solana/spl-token) - A package to work with spl tokens * [Mocha](https://mochajs.org/) - A JS testing tool ## Getting Started ### Prep work 🔪🥒 Use the CLI to set your network to devnet ``` solana config set --url devnet ``` To confirm if it worked check the output after entering the cmd ``` Config File: /Users/anoushkkharangate/.config/solana/cli/config.yml RPC URL: https://api.devnet.solana.com WebSocket URL: wss://api.devnet.solana.com/ (computed) Keypair Path: /Users/anoushkkharangate/.config/solana/id.json Commitment: confirmed ``` Next if you haven’t already set up a file system wallet using this guide → [Solana wallet docs](https://docs.solana.com/wallet-guide/file-system-wallet#generate-a-file-system-wallet-keypair) and also add some devnet sol using the command `solana airdrop 1` Lastly use anchor cli to make and anchor project ``` anchor init ``` Make sure that Anchor.toml is also set to devnet ``` [features] seeds = false [programs.devnet] metaplex_anchor_nft = "Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS" [registry] url = "https://anchor.projectserum.com" [provider] cluster = "devnet" wallet = "/Users//.config/solana/id.json" [scripts] test = "yarn run ts-mocha -p ./tsconfig.json -t 1000000 tests/**/*.ts" ``` That’s it now your all set to eat glass! ## Step 1 - Import the Dependencies 📦 In your project there must be folder called programs, go to `programs//Cargo.toml` and add these dependencies. Make sure to use version `0.22.1` and you can use [avm](https://book.anchor-lang.com/chapter_5/avm.html) to change it ``` [dependencies] anchor-lang = "0.22.1" anchor-spl = "0.22.1" mpl-token-metadata = {version = "1.2.5", features = ["no-entrypoint"]} ``` > 💫 Don’t use latest version of anchor and because anchor holds off updating itself with the latest version of solana-program it might cause conflicts between dependency requirements of the mpl crate and the anchor crates Then go to the lib.rs file in src and import these ``` use anchor_lang::prelude::*; use anchor_lang::solana_program::program::invoke; use anchor_spl::token; use anchor_spl::token::{MintTo, Token}; use mpl_token_metadata::instruction::{create_master_edition_v3, create_metadata_accounts_v2}; ``` Cool now we can write the mint function! ## Step 2 - Writing the Mint Function Struct 🏗 First let’s create the accounts struct for mint function ``` #[derive(Accounts)] pub struct MintNFT<'info> { #[account(mut)] pub mint_authority: Signer<'info>, /// CHECK: This is not dangerous because we don't read or write from this account #[account(mut)] pub mint: UncheckedAccount<'info>, // #[account(mut)] pub token_program: Program<'info, Token>, /// CHECK: This is not dangerous because we don't read or write from this account #[account(mut)] pub metadata: UncheckedAccount<'info>, /// CHECK: This is not dangerous because we don't read or write from this account #[account(mut)] pub token_account: UncheckedAccount<'info>, /// CHECK: This is not dangerous because we don't read or write from this account pub token_metadata_program: UncheckedAccount<'info>, /// CHECK: This is not dangerous because we don't read or write from this account #[account(mut)] pub payer: AccountInfo<'info>, pub system_program: Program<'info, System>, /// CHECK: This is not dangerous because we don't read or write from this account pub rent: AccountInfo<'info>, /// CHECK: This is not dangerous because we don't read or write from this account #[account(mut)] pub master_edition: UncheckedAccount<'info>, } ``` Don’t worry about the Unchecked accounts as we will pass these into the Metaplex program which will check it for us. In order to use Unchecked accounts in Anchor yo need to add this comment above each account ``` /// CHECK: This is not dangerous because we don't read or write from this account ``` ## Step 3 - The Mint Function 🪙 Let’s make a function that uses the struct we just made to mint the token ``` pub fn mint_nft( ctx: Context, creator_key: Pubkey, uri: String, title: String, ) -> Result<()> { msg!("Initializing Mint NFT"); let cpi_accounts = MintTo { mint: ctx.accounts.mint.to_account_info(), to: ctx.accounts.token_account.to_account_info(), authority: ctx.accounts.payer.to_account_info(), }; msg!("CPI Accounts Assigned"); let cpi_program = ctx.accounts.token_program.to_account_info(); msg!("CPI Program Assigned"); let cpi_ctx = CpiContext::new(cpi_program, cpi_accounts); msg!("CPI Context Assigned"); token::mint_to(cpi_ctx, 1)?; msg!("Token Minted !!!"); let account_info = vec![ ctx.accounts.metadata.to_account_info(), ctx.accounts.mint.to_account_info(), ctx.accounts.mint_authority.to_account_info(), ctx.accounts.payer.to_account_info(), ctx.accounts.token_metadata_program.to_account_info(), ctx.accounts.token_program.to_account_info(), ctx.accounts.system_program.to_account_info(), ctx.accounts.rent.to_account_info(), ]; msg!("Account Info Assigned"); let creator = vec![ mpl_token_metadata::state::Creator { address: creator_key, verified: false, share: 100, }, mpl_token_metadata::state::Creator { address: ctx.accounts.mint_authority.key(), verified: false, share: 0, }, ]; msg!("Creator Assigned"); let symbol = std::string::ToString::to_string("symb"); invoke( &create_metadata_accounts_v2( ctx.accounts.token_metadata_program.key(), ctx.accounts.metadata.key(), ctx.accounts.mint.key(), ctx.accounts.mint_authority.key(), ctx.accounts.payer.key(), ctx.accounts.payer.key(), title, symbol, uri, Some(creator), 1, true, false, None, None, ), account_info.as_slice(), )?; msg!("Metadata Account Created !!!"); let master_edition_infos = vec![ ctx.accounts.master_edition.to_account_info(), ctx.accounts.mint.to_account_info(), ctx.accounts.mint_authority.to_account_info(), ctx.accounts.payer.to_account_info(), ctx.accounts.metadata.to_account_info(), ctx.accounts.token_metadata_program.to_account_info(), ctx.accounts.token_program.to_account_info(), ctx.accounts.system_program.to_account_info(), ctx.accounts.rent.to_account_info(), ]; msg!("Master Edition Account Infos Assigned"); invoke( &create_master_edition_v3( ctx.accounts.token_metadata_program.key(), ctx.accounts.master_edition.key(), ctx.accounts.mint.key(), ctx.accounts.payer.key(), ctx.accounts.mint_authority.key(), ctx.accounts.metadata.key(), ctx.accounts.payer.key(), Some(0), ), master_edition_infos.as_slice(), )?; msg!("Master Edition Nft Minted !!!"); Ok(()) } ``` > 💫 If you want debug your program better use `msg!()` to log whatever value you want to check, it accepts string so you’ll hv to use `std::string::ToString` to convert. Your logs will appear in the terminal or in `.anchor>program-logs>` ![path to logs](https://images.mirror-media.xyz/publication-images/f0cg9s4Tskm1E-qzeUBl0.png?height=196&width=772) ### So a few things here… The creators array needs to have the person minting the nfts as part of it, but you can set the share as 0 so it doesn’t really matter ``` let creator = vec![ mpl_token_metadata::state::Creator { address: creator_key, verified: false, share: 100, }, mpl_token_metadata::state::Creator { address: ctx.accounts.mint_authority.key(), verified: false, share: 0, }, ]; ``` I haven’t implemented Collections as it’s not in the scope of this guide but u can do it by using `mpl_token_metadata::instruction::set_and_verify_collection` Regarding why I’ve set Max supply to 0 here. In Metaplex if the token is meant to be one of a kind then you have to set it’s max supply to zero since total supply - supply claimed (1-1) equals 0 ``` &create_master_edition_v3( ctx.accounts.token_metadata_program.key(), ctx.accounts.master_edition.key(), ctx.accounts.mint.key(), ctx.accounts.payer.key(), ctx.accounts.mint_authority.key(), ctx.accounts.metadata.key(), ctx.accounts.payer.key(), Some(0), // max supply 0 ), ``` Once you’ve written the function run `anchor build && anchor deploy` and you should see the deployed Program ID ![](https://images.mirror-media.xyz/publication-images/7qTFUj2GL4Po9b3wYxon-.png?height=468&width=2052) paste this program ID in your Anchor.toml and lib.rs file wherever you see this default ID `Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS` ## Step 4 - Calling the Mint Function 🤙 Before doing anything make sure that you have imported `@solana/web3.js` and `@solana/spl-token`. Inside `tests/.ts` add these imports and constants ``` import { TOKEN_PROGRAM_ID, createAssociatedTokenAccountInstruction, getAssociatedTokenAddress, createInitializeMintInstruction, MINT_SIZE, } from "@solana/spl-token"; import { LAMPORTS_PER_SOL } from "@solana/web3.js"; const { PublicKey, SystemProgram } = anchor.web3; q ``` ``` const TOKEN_METADATA_PROGRAM_ID = new anchor.web3.PublicKey( "metaqbxxUerdq28cj1RbAWkYQm3ybzjb6a8bt518x1s" ); const lamports: number = await program.provider.connection.getMinimumBalanceForRentExemption( MINT_SIZE ); const getMetadata = async ( mint: anchor.web3.PublicKey ): Promise => { return ( await anchor.web3.PublicKey.findProgramAddress( [ Buffer.from("metadata"), TOKEN_METADATA_PROGRAM_ID.toBuffer(), mint.toBuffer(), ], TOKEN_METADATA_PROGRAM_ID ) )[0]; }; const getMasterEdition = async ( mint: anchor.web3.PublicKey ): Promise => { return ( await anchor.web3.PublicKey.findProgramAddress( [ Buffer.from("metadata"), TOKEN_METADATA_PROGRAM_ID.toBuffer(), mint.toBuffer(), Buffer.from("edition"), ], TOKEN_METADATA_PROGRAM_ID ) )[0]; }; const mintKey: anchor.web3.Keypair = anchor.web3.Keypair.generate(); ``` Now lets make the token and the associated token account ``` const NftTokenAccount = await getAssociatedTokenAddress( mintKey.publicKey, program.provider.wallet.publicKey ); console.log("NFT Account: ", NftTokenAccount.toBase58()); const mint_tx = new anchor.web3.Transaction().add( anchor.web3.SystemProgram.createAccount({ fromPubkey: program.provider.wallet.publicKey, newAccountPubkey: mintKey.publicKey, space: MINT_SIZE, programId: TOKEN_PROGRAM_ID, lamports, }), createInitializeMintInstruction( mintKey.publicKey, 0, program.provider.wallet.publicKey, program.provider.wallet.publicKey ), createAssociatedTokenAccountInstruction( program.provider.wallet.publicKey, NftTokenAccount, program.provider.wallet.publicKey, mintKey.publicKey ) ); const res = await program.provider.send(mint_tx, [mintKey]); console.log( await program.provider.connection.getParsedAccountInfo(mintKey.publicKey) ); console.log("Account: ", res); console.log("Mint key: ", mintKey.publicKey.toString()); console.log("User: ", program.provider.wallet.publicKey.toString()); const metadataAddress = await getMetadata(mintKey.publicKey); const masterEdition = await getMasterEdition(mintKey.publicKey); console.log("Metadata address: ", metadataAddress.toBase58()); console.log("MasterEdition: ", masterEdition.toBase58()); ``` > **Note:** the mint and freeze authority has to be same otherwise it doesn’t work > > ``` > createInitializeMintInstruction( > mintKey.publicKey, > 0, > program.provider.wallet.publicKey,// mint auth > program.provider.wallet.publicKey // freeze auth > ), > ``` Now call the mint function and pass all the data and accounts ``` const tx = await program.rpc.mintNft( mintKey.publicKey, "https://arweave.net/y5e5DJsiwH0s_ayfMwYk-SnrZtVZzHLQDSTZ5dNRUHA", "NFT Title", { accounts: { mintAuthority: program.provider.wallet.publicKey, mint: mintKey.publicKey, tokenAccount: NftTokenAccount, tokenProgram: TOKEN_PROGRAM_ID, metadata: metadataAddress, tokenMetadataProgram: TOKEN_METADATA_PROGRAM_ID, payer: program.provider.wallet.publicKey, systemProgram: SystemProgram.programId, rent: anchor.web3.SYSVAR_RENT_PUBKEY, masterEdition: masterEdition, }, } ); console.log("Your transaction signature", tx); ``` That’s it! Now just run anchor test and you should be able to mint your nft ``` Account: 4swRFMNovHCkXY3gDgAGBXZwpfFuVyxWpWsgXqbYvoZG1M63nZHxyPRm7KTqAjSdTpHn2ivyPr6jQfxeLsB6a1nX Mint key: DehGx61vZPYNaMWm9KYdP91UYXXLu1XKoc2CCu3NZFNb User: 7CtWnYdTNBb3P9eViqSZKUekjcKnMcaasSMC7NbTVKuE Metadata address: 7ut8YMzGqZAXvRDro8jLKkPnUccdeQxsfzNv1hjzc3Bo MasterEdition: Au76v2ZDnWSLj23TCu9NRVEYWrbVUq6DAGNnCuALaN6o Your transaction signature KwEst87H3dZ5GwQ5CDL1JtiRKwcXJKNzyvQShaTLiGxz4HQGsDA7EW6rrhqwbJ2TqQFRWzZFvhfBU1CpyYH7WhH ✔ Is initialized! (6950ms) 1 passing (7s) ✨ Done in 9.22s. ``` > 💫 If you get any custom program error with a hex value like 0x1, convert the hex value to plain text then go to [metaplex github](https://github.com/metaplex-foundation/metaplex-program-library/blob/45a97b2edbfd6aff34df4ee3e56194008f71bba7/token-metadata/program/src/error.rs) and search using your browser for the number + 1 th appearance of the word “error(“ You can checkout the NFT here [https://solscan.io/token/DehGx61vZPYNaMWm9KYdP91UYXXLu1XKoc2CCu3NZFNb?cluster=devnet](https://solscan.io/token/DehGx61vZPYNaMWm9KYdP91UYXXLu1XKoc2CCu3NZFNb?cluster=devnet) ## Wrapping up I hope this guide was useful for all the solana degens out there, when i first tried to mint an nft i was pulling my hair out but it slowly started to make sense once some fellow glass eaters explained it to me, hopefully i’ve made it that much easier for you. Here’s the github for this project👇 [https://github.com/anoushk1234/metaplex-anchor-nft](https://github.com/anoushk1234/metaplex-anchor-nft) You can follow me on my [twitter](https://twitter.com/anoushk77) and [github](https://github.com/anoushk1234), until next time keep eating glass!