Match overview in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the match expression in Rust?

The match expression in Rust allows you to compare a value against a series of patterns and execute code based on which pattern matches. It's similar to a switch statement but more powerful and exhaustive.

beginner

How does Rust ensure all cases are handled in a match expression?

Rust requires that match expressions be exhaustive, meaning all possible cases must be covered. If not, the compiler will give an error. You can use a catch-all pattern _ to handle any remaining cases.

beginner

What is the purpose of the underscore _ pattern in a match?

The underscore _ pattern acts as a wildcard that matches any value not matched by previous arms. It is used as a catch-all to ensure exhaustiveness without specifying every possible value.

intermediate

Can match arms bind variables? Give an example.

Yes, match arms can bind variables to parts of the matched value. For example:<br>

match some_option {
    Some(x) => println!("Value is {}", x),
    None => println!("No value"),
}

beginner

What happens if no match arm matches and there is no catch-all?

The Rust compiler will produce an error because match expressions must be exhaustive. You must handle all possible cases or include a catch-all _ arm.

What keyword is used in Rust to compare a value against multiple patterns?

A match

B switch

C case

D select

Rust uses the match keyword to compare a value against patterns.

What does the underscore _ pattern represent in a match?

A A variable binding

B A wildcard matching any value

C A specific value

D An error case

The underscore _ is a wildcard pattern that matches any value not matched before.

What will happen if a match expression is not exhaustive?

A It will ignore unmatched cases silently

B It will run but skip unmatched cases

C It will panic at runtime

D It will cause a compiler error

Rust requires match expressions to be exhaustive; otherwise, the compiler throws an error.

Can you bind variables inside match arms?

A Yes, to parts of the matched value

B Only in the catch-all arm

C Only constants can be used

D No, variables cannot be bound

You can bind variables to parts of the matched value inside match arms.

Which of these is a valid match arm pattern?

A case x

B default

C Some(x)

D switch(x)

Some(x) is a valid pattern matching an enum variant with a variable binding.

Explain how the match expression works in Rust and why it is useful.

Think about how you decide what to do based on different cases.

Describe the role of the underscore _ pattern in a match expression.

It’s like saying 'anything else' in a list of options.