anchor

Anchor ⚓

Anchor is a framework for Solana's Sealevel runtime providing several convenient developer tools.

• Rust eDSL for writing Solana programs
• IDL specification
• TypeScript package for generating clients from IDL
• CLI and workspace management for developing complete applications

If you're familiar with developing in Ethereum's Solidity, Truffle, web3.js or Parity's Ink!, then the experience will be familiar. Although the DSL syntax and semantics are targeted at Solana, the high level flow of writing RPC request handlers, emitting an IDL, and generating clients from IDL is the same.

Getting Started

For a quickstart guide and in depth tutorials, see the guided documentation. To jump straight to examples, go here. For the latest Rust API documentation, see docs.rs.

Note

• Anchor is in active development, so all APIs are subject to change.
• This code is unaudited. Use at your own risk.

Examples

Build stateful programs on Solana by defining a state struct with associated methods. Here's a classic counter example, where only the designated authority can increment the count.

#[program]
mod counter {

    #[state]
    pub struct Counter {
      authority: Pubkey,
      count: u64,
    }

    pub fn new(ctx: Context<Auth>) -> Result<Self> {
        Ok(Self {
            auth: *ctx.accounts.authority.key
        })
    }

    pub fn increment(&mut self, ctx: Context<Auth>) -> Result<()> {
        if &self.authority != ctx.accounts.authority.key {
            return Err(ErrorCode::Unauthorized.into());
        }

        self.count += 1;

        Ok(())
    }
}

#[derive(Accounts)]
pub struct Auth<'info> {
    #[account(signer)]
    authority: AccountInfo<'info>,
}

#[error]
pub enum ErrorCode {
    #[msg("You are not authorized to perform this action.")]
    Unauthorized,
}

Additionally, one can utilize the full power of Solana's parallel execution model by keeping the program stateless and working with accounts directly. The above example can be rewritten as follows.

use anchor::prelude::*;

// Define instruction handlers.

#[program]
mod counter {
    use super::*;

    pub fn initialize(ctx: Context<Initialize>, authority: Pubkey) -> ProgramResult {
        let counter = &mut ctx.accounts.counter;

        counter.authority = authority;
        counter.count = 0;

        Ok(())
    }

    pub fn increment(ctx: Context<Update>) -> ProgramResult {
        let counter = &mut ctx.accounts.counter;

        counter += 1;

        Ok(())
    }
}

// Define accounts for each handler.

#[derive(Accounts)]
pub struct Initialize<'info> {
    #[account(init)]
    pub counter: ProgramAccount<'info, Counter>,
    pub rent: Sysvar<'info, Rent>,
}

#[derive(Accounts)]
pub struct Increment<'info> {
    #[account(mut, has_one = authority)]
    pub counter: ProgramAccount<'info, Counter>,
    #[account(signer)]
    pub authority: AccountInfo<'info>,
}

// Define program owned accounts.

#[account]
pub struct Counter {
    pub authority: Pubkey,
    pub count: u64,
}

Due to the fact that account sizes on Solana are fixed, some combination of the above is often required. For example, one can store store global state associated with the entire program in the #[state] struct and local state assocated with each user in individual #[account] structs.

Accounts attribute syntax.

There are several inert attributes (attributes that are consumed only for the purposes of the Accounts macro) that can be specified on a struct deriving Accounts.

Attribute	Where Applicable	Description
#[account(signer)]	On raw AccountInfo structs.	Checks the given account signed the transaction.
#[account(mut)]	On AccountInfo, ProgramAccount or CpiAccount structs.	Marks the account as mutable and persists the state transition.
#[account(init)]	On ProgramAccount structs.	Marks the account as being initialized, skipping the account discriminator check.
#[account(belongs_to = <target>)]	On ProgramAccount or CpiAccount structs	Checks the target field on the account matches the target field in the struct deriving Accounts.
#[account(has_one = <target>)]	On ProgramAccount or CpiAccount structs	Semantically different, but otherwise the same as belongs_to.
#[account(seeds = [<seeds>])]	On AccountInfo structs	Seeds for the program derived address an AccountInfo struct represents.
#[account(owner = program \| skip)]	On AccountInfo structs	Checks the owner of the account is the current program or skips the check.
#[account("<literal>")]	On any type deriving Accounts	Executes the given code literal as a constraint. The literal should evaluate to a boolean.
#[account(rent_exempt = <skip>)]	On AccountInfo or ProgramAccount structs	Optional attribute to skip the rent exemption check. By default, all accounts marked with #[account(init)] will be rent exempt, and so this should rarely (if ever) be used. Similarly, omitting = skip will mark the account rent exempt.

License

Anchor is licensed under Apache 2.0.