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Solana Mobile: RPC, Tokens, NFTs & Program Interaction

Solana Mobile: RPC, Tokens, NFTs & Program Interaction

SPL Token Operations on Mobile

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Tokens on Solana

Everything on Solana is an account. Tokens follow the same model, but with extra structure. Understanding this model is essential before you write mobile token code.

A token has three key accounts:

  • Mint Account: Defines the token (decimals, supply, authorities)

  • Token Account: Holds a user's balance of that token

  • Metadata Account: Stores name, symbol, image (via Token Metadata program)

When a user wants to hold USDC, they need a Token Account that links their wallet to the USDC Mint Account. This is called an Associated Token Account (ATA).

text
Wallet → Token Account → Mint Account
(owner)   (balance)      (token definition)

Setting Up SPL Token

Install the SPL Token library:

shellscript
yarn add @solana/spl-token

The library provides instructions for all token operations. On mobile, you'll typically:

  1. Build the instruction

  2. Create a transaction

  3. Sign with MWA

  4. Send and confirm

typescript
import {
  getAssociatedTokenAddress,
  createTransferInstruction,
  TOKEN_PROGRAM_ID,
  ASSOCIATED_TOKEN_PROGRAM_ID,
} from "@solana/spl-token";
import {
  Connection,
  PublicKey,
  Transaction,
  TransactionMessage,
  VersionedTransaction,
} from "@solana/web3.js";

Checking Token Balances

Before any transfer, check the user's balance:

typescript
async function getTokenBalance(
  connection: Connection,
  walletAddress: PublicKey,
  mintAddress: PublicKey
): Promise<number> {
  // Derive the Associated Token Account address
  const ata = await getAssociatedTokenAddress(
    mintAddress,
    walletAddress
  );

  try {
    const accountInfo = await connection.getTokenAccountBalance(ata);
    return parseFloat(accountInfo.value.uiAmountString || "0");
  } catch (error) {
    // Account doesn't exist = zero balance
    return 0;
  }
}

// Usage
const USDC_MINT = new PublicKey("EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v");
const balance = await getTokenBalance(connection, userWallet, USDC_MINT);
console.log(`USDC Balance: ${balance}`);

Fetching All Token Balances

For a portfolio view, fetch all tokens at once:

typescript
async function getAllTokenBalances(
  connection: Connection,
  walletAddress: PublicKey
): Promise<TokenBalance[]> {
  const tokenAccounts = await connection.getParsedTokenAccountsByOwner(
    walletAddress,
    { programId: TOKEN_PROGRAM_ID }
  );

  return tokenAccounts.value.map((account) => {
    const info = account.account.data.parsed.info;
    return {
      mint: info.mint,
      balance: info.tokenAmount.uiAmount,
      decimals: info.tokenAmount.decimals,
      address: account.pubkey.toBase58(),
    };
  });
}

Building Transfer Transactions

Here's how to build a token transfer that you'll sign with MWA:

typescript
import { transact } from "@solana-mobile/mobile-wallet-adapter-protocol-web3js";

async function transferToken(
  connection: Connection,
  fromWallet: PublicKey,
  toWallet: PublicKey,
  mintAddress: PublicKey,
  amount: number,
  decimals: number
): Promise<string> {
  // 1. Derive token accounts
  const fromAta = await getAssociatedTokenAddress(mintAddress, fromWallet);
  const toAta = await getAssociatedTokenAddress(mintAddress, toWallet);

  // 2. Check if recipient has a token account
  const toAtaInfo = await connection.getAccountInfo(toAta);
  
  // 3. Build instructions
  const instructions = [];
  
  // Create recipient's ATA if it doesn't exist
  if (!toAtaInfo) {
    instructions.push(
      createAssociatedTokenAccountInstruction(
        fromWallet,  // payer
        toAta,       // ATA address
        toWallet,    // owner
        mintAddress  // mint
      )
    );
  }

  // Add transfer instruction
  const rawAmount = Math.floor(amount * Math.pow(10, decimals));
  instructions.push(
    createTransferInstruction(
      fromAta,    // source
      toAta,      // destination
      fromWallet, // owner/signer
      rawAmount   // amount in smallest units
    )
  );

  // 4. Build transaction
  const { blockhash, lastValidBlockHeight } = 
    await connection.getLatestBlockhash("confirmed");

  const messageV0 = new TransactionMessage({
    payerKey: fromWallet,
    recentBlockhash: blockhash,
    instructions,
  }).compileToV0Message();

  const transaction = new VersionedTransaction(messageV0);

  // 5. Sign with MWA
  const signedTx = await transact(async (wallet) => {
    const authResult = await wallet.authorize({
      cluster: "mainnet-beta",
      identity: {
        name: "My Token App",
        uri: "https://myapp.com",
        icon: "favicon.ico",
      },
    });

    const [signedTransaction] = await wallet.signTransactions({
      transactions: [transaction],
    });

    return signedTransaction;
  });

  // 6. Send and confirm
  const signature = await connection.sendTransaction(signedTx);
  
  await connection.confirmTransaction({
    signature,
    blockhash,
    lastValidBlockHeight,
  }, "confirmed");

  return signature;
}

Creating Token Accounts

Sometimes you need to explicitly create a token account before receiving:

typescript
import {
  createAssociatedTokenAccountInstruction,
  getAssociatedTokenAddress,
} from "@solana/spl-token";

async function createTokenAccountIfNeeded(
  connection: Connection,
  payer: PublicKey,
  owner: PublicKey,
  mint: PublicKey
): Promise<PublicKey> {
  const ata = await getAssociatedTokenAddress(mint, owner);
  
  const ataInfo = await connection.getAccountInfo(ata);
  
  if (ataInfo) {
    // Already exists
    return ata;
  }

  // Need to create it
  const instruction = createAssociatedTokenAccountInstruction(
    payer,  // Who pays for the account creation
    ata,    // The ATA address
    owner,  // Who will own this token account
    mint    // The token mint
  );

  // Build and sign transaction...
  // (similar to transfer flow)

  return ata;
}

Cost Considerations

Creating an ATA costs ~0.002 SOL (rent exemption). In a transfer to a new recipient:

  1. You might pay to create their token account

  2. This is often expected in apps, good UX

  3. Consider showing users this cost before confirming

typescript
const RENT_EXEMPT_MINIMUM = 0.00203928; // SOL for a token account

// Show user the total cost
const transferCost = recipientNeedsAta 
  ? RENT_EXEMPT_MINIMUM + transactionFee 
  : transactionFee;

Token-2022 (Token Extensions)

Solana has a newer token program with additional features. Check which program a mint uses:

typescript
import { TOKEN_2022_PROGRAM_ID, TOKEN_PROGRAM_ID } from "@solana/spl-token";

async function getTokenProgram(
  connection: Connection,
  mintAddress: PublicKey
): Promise<PublicKey> {
  const mintInfo = await connection.getAccountInfo(mintAddress);
  
  if (!mintInfo) {
    throw new Error("Mint not found");
  }

  // Check which program owns the mint
  if (mintInfo.owner.equals(TOKEN_2022_PROGRAM_ID)) {
    return TOKEN_2022_PROGRAM_ID;
  }
  
  return TOKEN_PROGRAM_ID;
}

// Use the correct program in your instructions
const tokenProgram = await getTokenProgram(connection, mintAddress);

const transferIx = createTransferInstruction(
  sourceAta,
  destAta,
  owner,
  amount,
  [],
  tokenProgram  // Pass the correct program
);

Mobile UX Patterns

Loading States

Token operations take time. Show meaningful progress:

typescript
const [status, setStatus] = useState<
  "idle" | "building" | "signing" | "sending" | "confirming" | "done" | "error"
>("idle");

async function handleTransfer() {
  try {
    setStatus("building");
    const tx = await buildTransferTransaction(/* ... */);
    
    setStatus("signing");
    const signedTx = await signWithMwa(tx);
    
    setStatus("sending");
    const signature = await connection.sendTransaction(signedTx);
    
    setStatus("confirming");
    await connection.confirmTransaction(signature, "confirmed");
    
    setStatus("done");
  } catch (error) {
    setStatus("error");
    // Handle specific errors
  }
}

Amount Input

Always handle decimal precision carefully:

typescript
function parseTokenAmount(
  input: string,
  decimals: number
): bigint | null {
  // Remove anything except digits and decimal
  const cleaned = input.replace(/[^\d.]/g, "");
  
  // Validate format
  const parts = cleaned.split(".");
  if (parts.length > 2) return null;
  
  const wholePart = parts[0] || "0";
  const decimalPart = (parts[1] || "").padEnd(decimals, "0").slice(0, decimals);
  
  try {
    return BigInt(wholePart + decimalPart);
  } catch {
    return null;
  }
}

// Usage
const rawAmount = parseTokenAmount("10.5", 6); // USDC has 6 decimals
// Result: 10500000n

Max Button

Let users easily send their full balance:

typescript
function getMaxTransferAmount(
  balance: number,
  decimals: number,
  estimatedFee: number = 0.00005 // Conservative transaction fee
): number {
  // Leave a small buffer for fees
  // Note: token transfers don't cost tokens, but the user needs SOL for gas
  return Math.max(0, balance);
}

Error Handling

Token operations have specific failure modes:

typescript
try {
  await transferToken(/* ... */);
} catch (error) {
  const message = error.message || "";
  
  if (message.includes("insufficient funds")) {
    // Not enough tokens
    showError("Insufficient token balance");
  } else if (message.includes("insufficient lamports")) {
    // Not enough SOL for fees
    showError("Not enough SOL for transaction fees");
  } else if (message.includes("Account not found")) {
    // Token account doesn't exist
    showError("Token account not found");
  } else if (message.includes("owner does not match")) {
    // Wrong owner for the token account
    showError("Token account ownership mismatch");
  } else {
    showError("Transfer failed. Please try again.");
  }
}

Key Takeaways

  • Token Account model: Users need ATAs to hold tokens. Check if they exist before transfers.

  • Decimals matter: USDC is 6 decimals, SOL is 9. Always convert properly.

  • ATA creation costs SOL: Factor this into UX when sending to new recipients.

  • Check the token program: Token-2022 mints need the right program ID.

  • Show progress: Token operations have multiple steps; keep users informed.

Next, we'll build on these patterns to handle NFTs: tokens with supply of 1 and rich metadata.

Next LessonNFT Operations with DAS API on Mobile
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