Qu’est-ce qu’un trait ?

Sometimes many types need the same ability, like being printable. A trait lets you describe that shared behavior once. 🤝

Think of a trait as a contract: it lists the methods a type must provide, without saying how they work.

If you have met interfaces in other languages, a trait is the same idea. It names the required methods and nothing more.

You declare a trait with the trait keyword, then list method signatures inside it, much like a struct.

The ... body marks a method as required but unimplemented. The trait promises the method exists, not what it does.

A trait usually holds only signatures. The actual logic lives in each type that agrees to follow the contract.

Traits let you write code against a capability instead of a specific type. Any conforming type just works.

A Dog and a Robot can both promise to greet. They share the trait while keeping totally different internals.

Structs have no class-style inheritance, so traits are how Mojo shares behavior. They describe what, not a base type.

Mojo verifies trait conformance at compile time. If a type misses a required method, your build fails early.

Traits are the foundation for generic Mojo code. Master this contract idea and reusable, type-safe functions come next. 🧱

Let us pin down what a trait really is.

A trait is a contract of required methods. It describes shared behavior so many types can be used the same way. 🎯