Rust Date Parser: Handling user input and Parsing errors

Last update on December 21 2024 10:19:46 (UTC/GMT +8 hours)

Write a Rust program that accepts user input for a date, parses it, and prints it in a different format, handling parsing errors.

Sample Solution:

Rust Code:

use std::io;

fn main() {
    println!("Please enter a date in the format YYYY-MM-DD:");
    
    let mut input = String::new();
    io::stdin().read_line(&mut input).expect("Failed to read input.");
    
    // Trim any leading or trailing whitespace from the input
    let trimmed_input = input.trim();
    
    // Attempt to parse the input date
    match parse_date(trimmed_input) {
        Ok(parsed_date) => println!("Parsed date: {}", parsed_date),
        Err(err) => eprintln!("Error parsing date: {}", err),
    }
}

fn parse_date(date_str: &str) -> Result<String, &str> {
    // Attempt to split the date string into its components
    let parts: Vec<&str> = date_str.split('-').collect();
    
    // Check if the date string has three components
    if parts.len() != 3 {
        return Err("Invalid date format. Please use YYYY-MM-DD.");
    }
    
    // Attempt to parse the components into integers
    let year: i32 = match parts[0].parse() {
        Ok(year) => year,
        Err(_) => return Err("Invalid year."),
    };
    
    let month: u32 = match parts[1].parse() {
        Ok(month) if (1..=12).contains(&month) => month,
        _ => return Err("Invalid month."),
    };
    
    let day: u32 = match parts[2].parse() {
        Ok(day) if (1..=31).contains(&day) => day,
        _ => return Err("Invalid day."),
    };
    
    // Format the parsed date components
    let parsed_date = format!("{}-{:02}-{:02}", year, month, day);
    
    Ok(parsed_date)
}

Output:

Please enter a date in the format YYYY-MM-DD: 2000-02-02
Parsed date: 2000-02-02

Please enter a date in the format YYYY-MM-DD: 2001-13-12
   Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 0.65s
     Running `target/debug/playground`
Error parsing date: Invalid month.

Please enter a date in the format YYYY-MM-DD: 2001-02-32
  Compiling playground v0.0.1 (/playground)
    Finished dev [unoptimized + debuginfo] target(s) in 0.58s
     Running `target/debug/playground`
Error parsing date: Invalid day.

Explanation:

Here's a brief explanation of the above Rust code:

• The main function:
• Prints a message asking the user to enter a date.
• Reads the user input from the console.
• Trims any leading or trailing whitespace from the input.
• Calls the "parse_date()" function to attempt to parse the input date.
• Prints either the parsed date or an error message depending on the result of the parsing.
• The parse_date function:
• Attempts to split the input date string into its components (year, month, day) based on the '-' delimiter.
• Checks if the date string has exactly three components. If not, it returns an error indicating an invalid date format.
• Attempts to parse each component into integers (year, month, day).
• Validates the parsed year, month, and day:
• For the year, it checks if it can be parsed into an integer.
• For the month, it checks if it falls within the range of 1 to 12 (inclusive).
• For the day, it checks if it falls within the range 1 to 31 (inclusive).
• If any parsing or validation fails, it returns an error with an appropriate error message.
• If parsing and validation succeed, it formats the parsed date components into the YYYY-MM-DD format and returns it as a "String".

Rust Code Editor:

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