Using unwrap and expect in Rust - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the unwrap() method do in Rust?

unwrap() extracts the value inside an Option or Result if it exists. If the value is None or Err, it causes the program to panic and stop.

beginner

How is expect() different from unwrap()?

expect() works like unwrap() but lets you provide a custom error message that shows when the program panics.

intermediate

When should you prefer expect() over unwrap()?

Use expect() when you want to give a clear message about why the program failed. This helps debugging by explaining what went wrong.

beginner

What happens if you call unwrap() on a None value?

The program will panic and stop running, showing a default error message about calling unwrap() on a None value.

beginner

Show a simple Rust example using expect() with a custom error message.

<pre>let text = Some("hello");
let value = text.expect("Expected a string but found None");
println!("Value: {}", value);</pre>

What does unwrap() do when called on None?

A Panics and stops the program

B Returns a default value

C Returns <code>None</code>

D Ignores the error and continues

unwrap() panics if called on None because there is no value to extract.

Which method lets you add a custom panic message?

A expect()

B unwrap()

C unwrap_or()

D unwrap_or_else()

expect() lets you provide a custom message that shows when the program panics.

Why is it better to use expect() instead of unwrap() in some cases?

A Because <code>unwrap()</code> is slower

B Because <code>expect()</code> never panics

C Because <code>expect()</code> provides a clear error message

D Because <code>unwrap()</code> returns an Option

expect() helps debugging by showing a clear message when something goes wrong.

What type of Rust values can you call unwrap() on?

A Only <code>Option</code>

B <code>Option</code> and <code>Result</code>

C Any type

D Only <code>Result</code>

unwrap() works on both Option and Result types.

What is the risk of using unwrap() in your code?

A It can cause silent errors

B It changes the data type

C It slows down the program

D It can cause the program to panic unexpectedly

Using unwrap() can cause your program to panic and stop if the value is missing or an error.

Explain in your own words what unwrap() and expect() do in Rust and when you might use each.

Think about how they handle missing or error values.

Describe a situation where using expect() would be better than unwrap().

Consider how error messages help you find bugs.