How to get token account data from within the on-chain program?

Question

I'm using get_associated_token_address to get a token account but how to find out if it is valid or not? Any help please?

let payer_associated_token_account = get_associated_token_address(
    payer_account.unwrap().key,
    token_mint.unwrap().key
);

// how to get the data of above ATA?

Answer 1

In order to access the data of an account, it has to be expected as an account input to the instruction and provided as AccountInfo.

Once you have the token account info, it can be deserialized into its appropriate data structure with:

let mut data: &[u8] = &info.try_borrow_data()?;
let acc = TokenAccount::try_deserialize(&mut data)?;

If you are using anchor, this can all be done for you if you include the account in the instruction's account context struct:

#[derive(Accounts)]
pub struct MyInstruction<'info> {
    // ...
    pub token_acc: Account<'info, TokenAccount>,
    // ...
}

then accessing the token account data within the instruction simply becomes:

let amount = ctx.accounts.token_acc.amount;

(or whatever data you need to access)