cairo by example

naming convention

Cairo, like many other languages, has a clearly defined naming convention. It is advised to follow it since it’ll help both code writers and readers after getting used to it.

use core::debug::PrintTrait;

// Modules use snake_case naming.
mod sample_module {}

// Types use PascalCase. This includes enums, structs and traits and trait
// implementations.
type FeltAlias = felt252;

// Type parameters are types too, so they also use PascalCase, although they are
// generally single letters, like the `T` used here.
trait SomeAction<T> {
    fn trigger_action(self: T);

// Enum variants use PascalCase too:
enum MyEnum {
    VariantA: felt252,
    VariantB: (),

// However struct fields use snake_case instead.
struct MyStruct {
    field_a: felt252,
    field_b: u32,

// Functions and methods's names use snake_case.
fn a_method() {
    // The same naming convention applies to variables too.
    let local_variable = 1234;

impl MyStructImpl of SomeAction<MyStruct> {
    fn trigger_action(self: MyStruct) {

// Finally, constants are an exception as they use UPPER_CASE naming.
const A_CONSTANT: felt252 = 1234;

Usually, identifiers shouldn’t start with an underscore (_), however when they aren’t intended to be used they should start with _ so that the compiler understands the programmer’s intention and avoids emitting unused item warnings.

Try it out!
  1. Install the toolchain:
    • For macOS and Linux, run our script:
    • curl -sL | bash -s 2.2.0
    • For Windows and others, please see the official guide
  2. Run the example:
    1. Copy the example into a naming_convention.cairo file and run with:
    2. %!s(<nil>) naming_convention.cairo

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