rust-developer-guide.md

Rust Developer Guide

For Rust smart contracts, any no_std compatible crate (e.g., rand, alloc) can be used. Standard library crates are not supported. Verified libraries can be found on crates.io.

Prerequisites

Before getting started, ensure you have the following dependencies installed on your system:

• Clang and CMake: Install these if they are not already on your system.

• For macOS users, LLVM can be installed via Homebrew:

  brew install llvm

---

Install Fluent Scaffold CLI tool

To install the Fluent scaffold CLI tool, run the following command in your terminal:

cargo install gblend

To create a project, run the following in your terminal:

gblend init

After installing the Fluent build tool, you can initialize a new project and choose the Rust option to bootstrap the starter project.

Project Structure

.
├── Cargo.toml
└── lib.rs

Getting Started

In this guide, we will be working with the lib.rs file located in the src folder. The structure for any Rust smart contract will be as follows

lib.rs

// 1. Set the target to wasm32 and enable no_std for compatibility.
// no_std is required since WebAssembly's minimal runtime lacks support for Rust’s standard library.
#![cfg_attr(target_arch = "wasm32", no_std)]

// 2. Import FluentBase SDK
extern crate fluentbase_sdk;

use fluentbase_sdk::{basic_entrypoint, derive::Contract, SharedAPI};

// 3. Define Contract Struct with SDK: Acts as the core of the contract’s logic.
#[derive(Contract)]
struct GREETING<SDK> {
    sdk: SDK,
}

impl<SDK: SharedAPI> GREETING<SDK> {
    // 4. Deployment Logic: Placeholder for setup during deployment.
    fn deploy(&mut self) {
        // Add any custom deployment logic here
    }

    // 5. Core Contract Logic: writes "Hello, World" message to output.
    fn main(&mut self) {
        self.sdk.write("Hello, World".as_bytes());
    }
}

// 6. Set Entry Point: Connects GREETING struct to the WASM runtime.
basic_entrypoint!(GREETING);

This snippet shows how simple it is to interact with the Fluent VM: just call the SDK, initialize your contract, add the functions, and, if needed, define a custom deployment process. For an in-depth look, check this guide.

Compiling the Rust Smart Contract

Understanding the deployment process starts with comprehending the role of the Makefile. This file compiles Rust code into Wasm & rWasm and generates the necessary binaries that will be embedded in a tx for deployment.

gblend build rust -r

Executing this command compiles the code and generates a file named lib.wasm in the bin directory.

Deploying the Contract

To deploy contract, use gblend cli:

gblend deploy --private-key <PRIVATE_KEY> --dev lib.wasm --gas-limit 300000000

Upon successful deployment, the receipt of your deployment transaction will be displayed, confirming the smart contract deployment on Fluent using the Fluent SDK.

To view your deployed Fluent contract, navigate to the Fluent Devnet Explorer. From there, you can input your contract address to explore your deployed contract.