Parser Capstone

Key/Value Parser

Split Once and Validate

A small parser can convert raw text into structured parts while rejecting incomplete input.

Program

Play the program to choose an input string and parse it into a key/value pair.

key_value_pair_parser.rs 
fn main() {
    let input = ;
    match parse_pair(input) {
        Some((key, value)) => println!("{key}:{value}"),
        None => println!("invalid"),
    }
}

fn parse_pair(input: &str) -> Option<(&str, &str)> {
    let (key, value) = input.split_once('=')?;
    if key.is_empty() || value.is_empty() {
        None
    } else {
        Some((key, value))
    }
}

fn main() {
    let input = ;
    match parse_pair(input) {
        Some((key, value)) => println!("{key}:{value}"),
        None => println!("invalid"),
    }
}

fn parse_pair(input: &str) -> Option<(&str, &str)> {
    let (key, value) = input.split_once('=')?;
    if key.is_empty() || value.is_empty() {
        None
    } else {
        Some((key, value))
    }
}

fn main() {
    let input = ;
    match parse_pair(input) {
        Some((key, value)) => println!("{key}:{value}"),
        None => println!("invalid"),
    }
}

fn parse_pair(input: &str) -> Option<(&str, &str)> {
    let (key, value) = input.split_once('=')?;
    if key.is_empty() || value.is_empty() {
        None
    } else {
        Some((key, value))
    }
}
split_once `split_once('=')` separates the first key/value delimiter if it exists.
Option `?` returns `None` immediately when the delimiter is missing.
validation The parser rejects empty keys or values before returning structured data.