an example showing that 1 account can have multiple different data structures

multi-structure-account-anchor.rs

use anchor_lang::prelude::*;

declare_id!("8yBiqm4eZjDQACD5JnZrvoKB6nyE9xDh3yvMiPnWtTpL");

#[program]
pub mod multi_state_account_example {
    use super::*;

    pub fn create_many_faced_account_first_state(ctx: Context<CreateManyFacedAccount>, _account_bump:u8, first_hi1_to_add:u64, first_hi2_to_add:u32) -> ProgramResult {
        let new_state = State::FirstState {
            first_hi1: first_hi1_to_add,
            first_hi2: first_hi2_to_add
        };
        ctx.accounts.many_faced_pda.current = Some(new_state);
        msg!("created many faced account");
        match &ctx.accounts.many_faced_pda.current {
            Some(State::FirstState { first_hi1, first_hi2 }) => {
                msg!("first hi1: {}", first_hi1);
                msg!("first hi2: {}", first_hi2);
            }
            _ => return Err(ErrorCode::TestError.into())
        }
        Ok(())
    }

    pub fn update_many_faced_account_second_state(ctx: Context<UpdateManyFacedAccount>, _account_bump:u8, second_hi1_to_add:u32, second_hi2_to_add:u64) -> ProgramResult {
        let new_state = State::SecondState {
            second_hi1: second_hi1_to_add,
            second_hi2: second_hi2_to_add
        };
        ctx.accounts.many_faced_pda.current = Some(new_state);
        msg!("update many faced account");
        match &ctx.accounts.many_faced_pda.current {
            Some(State::SecondState { second_hi1, second_hi2 }) => {
                msg!("second hi1: {}", second_hi1);
                msg!("second hi2: {}", second_hi2);
            }
            _ => return Err(ErrorCode::TestError.into())
        }
        Ok(())
    }

    pub fn check_many_faced_account(ctx: Context<UpdateManyFacedAccount>, _account_bump:u8) -> ProgramResult {
        msg!("checking many faced account");
        match &ctx.accounts.many_faced_pda.current {
            Some(State::FirstState { first_hi1, first_hi2 }) => {
                msg!("it's a variant of FirstState");
                msg!("first hi1: {}", first_hi1);
                msg!("first hi2: {}", first_hi2);
            }
            Some(State::SecondState { second_hi1, second_hi2 }) => {
                msg!("it's a variant of SecondState");
                msg!("second hi1: {}", second_hi1);
                msg!("second hi2: {}", second_hi2);
            }
            _ => return Err(ErrorCode::TestError.into())
        }
        Ok(())
    }
}

#[error]
pub enum ErrorCode {
    TestError,
}

#[derive(Accounts)]
#[instruction(_account_bump:u8)]
pub struct CreateManyFacedAccount<'info> {
    #[account(
        init,
        payer = signer,
        space = 8 + 8 + 50,
        seeds = [b"many_faces".as_ref()],
        bump = _account_bump
    )]
    many_faced_pda: Account<'info, ManyFacedAccount>,
    signer: Signer<'info>,
    system_program: Program<'info, System>,
}

#[derive(Accounts)]
#[instruction(_account_bump:u8)]
pub struct UpdateManyFacedAccount<'info> {
    #[account(
        mut,
        seeds = [b"many_faces".as_ref()],
        bump = _account_bump
    )]
    many_faced_pda: Account<'info, ManyFacedAccount>,
    signer: Signer<'info>,
    system_program: Program<'info, System>,
}

#[account]
#[derive(Default)]
struct ManyFacedAccount {
    current: Option<State>
}
#[derive(AnchorSerialize, AnchorDeserialize, Clone)]
enum State {
    FirstState { first_hi1:u64, first_hi2:u32 },
    SecondState { second_hi1:u32, second_hi2:u64 }
}