Rust
Use Option for absence. Use Result for failure.
If nothing went wrong but a value may not exist, choose Option. If something tried to happen and can fail, choose Result.
A CLI always meets messy input. A user may skip an argument. A file path may be wrong. A number may not parse.
Rust makes you handle these cases before your project reaches the demo table. That is good. Your tool should print a clear message, not crash with a confusing panic.
0 of 7 lessons done · proved by a submitted project with a public repository
Here is a tiny CLI pattern using std::env::args. The first real argument may be missing, so nth(1) returns Option.
match forces you to handle both cases.
use std::env;
fn main() {
let name = env::args().nth(1);
match name {
Some(value) => println!("Hello, {value}"),
None => println!("Usage: cargo run -- <name>"),
}
}Reading a file can fail. The file may not exist, or your program may not have permission.
Return Result from a function, then use ? to pass the error upward instead of writing a match every time.
use std::fs;
use std::error::Error;
fn read_notes(path: &str) -> Result<String, Box<dyn Error>> {
let content = fs::read_to_string(path)?;
Ok(content)
}
fn main() -> Result<(), Box<dyn Error>> {
let content = read_notes("notes.txt")?;
println!("{content}");
Ok(())
}Beginners often use unwrap() because it makes the compiler quiet. It also makes your CLI crash when input is missing or invalid.
For a hackathon demo, unwrap() is risky. Use match for a friendly message, or return Result and use ? for real failures.
If you use ChatGPT or Gemini, ask for code that avoids unwrap() and returns Result from main. Then check the answer yourself.
Look for three things: Option is matched, fallible work returns Result, and ? is only used inside a function that returns Result or Option.
Prompt:
Convert this Rust CLI code to handle missing arguments and file read errors without unwrap(). Use Option, Result, match, and ? where suitable.Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.
0 of 5 done
Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.
0 of 5 done
Answer the quick check to finish this lesson.