Basic ink! Contract

Project Structure

Each ink! contract requires its own crate with two essential files:

• Cargo.toml: Project configuration and dependencies

• lib.rs: Contract implementation

💡 Tip You can use Swanky Suite to quickly bootstrap a new project. Check out the Swanky CLI guide for details.

Contract Configuration

Cargo.toml Setup

Your Cargo.toml should include the following sections:

[package]
name = "my_contract"
version = "0.1.0"
authors = ["Your Name <[email protected]>"]
edition = "2021"

[dependencies]
ink = { version = "4.3", default-features = false}
ink_metadata = { version = "4.3", features = ["derive"], optional = true }
scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive"] }
scale-info = { version = "2.5", default-features = false, features = ["derive"], optional = true }

[dev-dependencies]
ink_e2e = { version = "4.3" }

[lib]
path = "lib.rs"

[features]
default = ["std"]
std = [
    "ink/std",
    "scale/std",
    "scale-info/std"
]
ink-as-dependency = []
e2e-tests = []

Contract Implementation

Minimum Requirements

Every ink! contract must include:

⚠️ Required Elements

1. no_std attribute for non-standard library compilation

2. Contract module marked with #[ink::contract]

3. Storage struct with #[ink(storage)]

4. At least one constructor with #[ink(constructor)]

5. At least one message with #[ink(message)]

Basic Contract Template

#![cfg_attr(not(feature = "std"), no_std)]

#[ink::contract]
mod my_contract {
    /// Contract storage
    #[ink(storage)]
    pub struct MyContract {}

    impl MyContract {
        /// Contract constructor
        #[ink(constructor)]
        pub fn new() -> Self {
            Self {}
        }

        /// Contract message
        #[ink(message)]
        pub fn do_something(&self) {
            ()
        }
    }
}

Example Contracts

Flipper Contract

The flipper contract is the simplest example provided by the ink! team, perfect for understanding basic contract structure.

Best Practices

1. Project Organization

   • Keep one contract per crate

   • Use meaningful names for contract modules

   • Organize tests in a separate module

2. Code Structure

   • Group related functionality together

   • Document your code with comments

   • Follow Rust naming conventions

3. Testing

   • Include unit tests

   • Add integration tests where needed

   • Use ink!'s testing utilities