Using Rust for Smart Contracts

Setting up

Let’s first install the Solana CLI:

sh -c "$(curl -sSfL <https://release.solana.com/stable/install>)"

Now, we can create a new directory, and a solana wallet keypair:

mkdir ~/my-solana-wallet

solana-keygen new --outfile ~/my-solana-wallet/keypair.json

Now that we have a wallet, we can create a cluster on devnet, and add some test SOL to our wallet:

solana config set --url <https://api.devnet.solana.com>

solana airdrop

Writing the Code

Let’s first create a new project using Cargo in our local directory. This will come with all of the files we need to start building a smart contract

cargo init hello_world --lib

cd hello_world

Open up your Cargo.toml file and add the following code snippets at the bottom:

[lib]
name = "hello_world"
crate-type = ["cdylib", "lib"]

Now, navigate to “src/lib.rs” and open up the file. This is where we will create our Solana smart contract.

Step 1 is to import solana_program and create an entrypoint for our code.

use solana_program::{
    account_info::AccountInfo,
    entrypoint,
    entrypoint::ProgramResult,
    pubkey::Pubkey,
    msg,
};

entrypoint!(process_instruction)

Here, we import a few key aspects of solana_program and call the method entrypoint. This defines the first function to be called when our contract is run, which in our case is process_instruction.

Let’s now create the process_instruction function.

pub fn process_instruction(
	program_id; &Pubkey,
	accounts: &[AccountInfo],
	instruction_data: &[u8]
) -> ProgramResult {
	msg!("Hello World!");

Ok(()); 

}

We define process_instruction as a public function using pub fn, which takes in 3 parameters and returns a ProgramResult. This will call the method msg!, which prints “Hello World!” to the console. We then call the Ok(()) method to validate that our code ran successfully.

Deploying our Code

We can build our code using cargo, and deploy it with the solana cli:

cargo build-bpf

solana program deploy ./target/deploy/hello_world.so

Once you run this command, a programID will be returned (hence the ProgramResult in the process_instruction function.