In Rust program how to get an account's mint token balance (not SOL balance)

Question

Within my Rust program I would like to get the mint token balance of an account. I found the spl_token sdk but it only has functions to convert from a balance to a ui balance. I saw that an account has an amount field but this seems to be for the SOL amount or am I wrong?

Answer 1

Assuming Anchor.

#[account(
mut,
associated_token::mint=mint,
associated_token::authority=user,
)]
pub user_token_account: Box<Account<'info, TokenAccount>>,

user_token_account.amount

The SOL is accessed by lamports().

You can use reload after the CPI to get the updated value.

https://book.anchor-lang.com/anchor_in_depth/CPIs.html#reloading-an-account

Answer 2

In case you are using pure Solana Rust and not Anchor, this is how to do it, assuming Token-2022 program:

use spl_token_2022::{
    state::Account,
    extension::StateWithExtensions,
};

// ATA => Associated Token Account
// ata_info => &AccountInfo
// mint_info => &AccountInfo
let ata_data = ata_info.data.borrow();
let ata_state = StateWithExtensions::<Account>::unpack(&ata_data)?;

// Always check if you got the correct ATA for the mint
if &ata_state.base.mint != &mint_info.key {
    msg!("Token account doesn't match the expected mint");
    return Err(ProgramError::InvalidArgument);
}

msg!("balance={}", ata_state.base.amount);

For reference, the deserialized struct from the associated token account looks like this:

StateWithExtensions {
  base: Account {
    mint: 5zpRyR6d3cd3kBvkcjvqsLqQqPzoCbuyLtBTaE6mSvH3,
    owner: 7Lf9P1Ez7KuevTi2fgB8E4XRAMEWg74d7W2nbteT5oHW,
    amount: 1,
    delegate: None,
    state: Frozen,
    is_native: None,
    delegated_amount: 0,
    close_authority: None
  },
  tlv_data: [7, 0, 0, 0]
} 

In case you are still using the old Token program:

use spl_token::state::Account;

// ATA => Associated Token Account
// ata_info => &AccountInfo
// mint_info => &AccountInfo
let ata_data = ata_info.data.borrow();
let ata_state = Account::unpack(&ata_data)?;

// Always check if you got the correct ATA for the mint
if &ata_state.mint != &mint_info.key {
    msg!("Token account doesn't match the expected mint");
    return Err(ProgramError::InvalidArgument);
}

msg!("balance={}", ata_state.amount);

The struct stored in ata_state has the following shape:

pub struct Account {
    pub mint: Pubkey,
    pub owner: Pubkey,
    pub amount: u64,
    pub delegate: COption<Pubkey>,
    pub state: AccountState,
    pub is_native: COption<u64>,
    pub delegated_amount: u64,
    pub close_authority: COption<Pubkey>,
}