Default method implementations in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a default method implementation in Rust traits?

A default method implementation in Rust traits is a method defined inside a trait with a body. Types implementing the trait can use this default method without needing to provide their own version.

beginner

How do you override a default method implementation in Rust?

To override a default method, the implementing type provides its own method with the same name and signature inside the impl block for the trait.

intermediate

Why are default method implementations useful in Rust?

They allow trait authors to provide common behavior that many types can share, reducing code duplication and making it easier to add new methods without breaking existing implementations.

beginner

Can a trait have methods without default implementations?

Yes. Traits can have methods without default implementations, which must be implemented by any type that implements the trait.

beginner

Show a simple Rust trait with a default method implementation.

```rust
trait Greet {
    fn say_hello(&self) {
        println!("Hello from default method!");
    }
}

struct Person;

impl Greet for Person {}

fn main() {
    let p = Person;
    p.say_hello(); // Prints: Hello from default method!
}
```

What happens if a type implementing a trait does NOT override a default method?

A The default method implementation is used.

B Compilation fails with an error.

C The method is ignored and not available.

D The program crashes at runtime.

If a type does not override a default method, Rust uses the default implementation provided in the trait.

Which keyword is used to define a trait in Rust?

A fn

B struct

C impl

D trait

The keyword 'trait' is used to define traits in Rust.

Can a default method in a trait call other methods of the same trait?

A No, it can only use its own code.

B Yes, including methods without default implementations.

C Only if those methods are also default methods.

D Only if the trait is marked as 'default'.

Default methods can call other trait methods, even those without default implementations, allowing flexible behavior.

What must a type do if a trait method has no default implementation?

A Nothing, it can skip implementing it.

B Mark the method as optional.

C Provide its own implementation of that method.

D Use the default method from another trait.

If a trait method has no default implementation, the implementing type must provide its own version.

Which of these is a benefit of default method implementations?

A They allow code reuse and easier trait evolution.

B They force all types to implement every method.

C They prevent overriding methods.

D They make traits slower to compile.

Default methods help reuse code and let traits evolve without breaking existing implementations.

Explain what default method implementations are in Rust traits and why they are useful.

Think about how traits can provide behavior without forcing every type to write the same code.

Describe how you would override a default method implementation in a Rust trait for a specific type.

Consider how you customize behavior for your own types.