[FIXED] How to create a Hashmap containing a vector of Regex options for each line in a file in Rust

Issue

I am a Rust noob with a medium level knowledge of programming in general and have been stuck in this spot for quite a while. Essentially, I am reading from a file and performing regex to break up each line into groups that I want to process later. I am hoping to save each line in a hashmap as a vector of its groups, with the key of the hashmap being group 4.

I want to use a String to allow me to assign a value inside the for loop, but the captures_iter function is expecting a &str.

I am open to alternative solutions.

I alternate between two errors, and do not know a way around one without causing the other.

use std::fs::File;
use std::io::{BufRead, BufReader};
use regex::Regex;
use regex::Captures;
use std::collections::HashMap;

fn main() {
    //read file
    let input = File::open("../input.txt").unwrap();
    let reader = BufReader::new(input);

    //ugly regex, but it does exactly what I want it to
    let re = Regex::new(r"(?:(^[[:lower:]]+|^\d+) |)(?:([[:lower:]]+|[[:upper:]]+) |)(?:([[:lower:]]+|[[:upper:]]+|\d+|) |)-> ([[:lower:]]+)$").unwrap();
    
    //hashmap to store the 'instructions' which is the regex groups, with the key of group 4
    let mut instructions : HashMap<&str, Vec<&str>> = HashMap::new();

    for line in reader.lines().into_iter() {

        let line = line.unwrap();
        println!("Line Read: {}", line);

        for caps in re.captures_iter(&line){ //this line is where I am having touble, with or without the '&' before line, I get a different error

            let groups: Vec<&str> = caps.iter()
                .map(|m| match m {
                    Some(value) => value.as_str(),
                    None => ""
                })
            .collect();

            println!("{:?}", groups); //this prints exactly what I want

            instructions.insert(groups[4], groups); //this line is the one that causes the error, because of a reference outside the loop?
        }
    }
}

The error when line: for caps in re.captures_iter(&line){ is line does not live long enough

The error when line: for caps in re.captures_iter(line){ is mismatched types

I appreciate any help or advice. Please let me know if I can provide any more information.

P.S. This is for Advent of Code 2015, day 7. If you think I am going about this the complete wrong way also feel free to let me know.

Solution

You can make the groups to be a Vec<String> instead of Vec<&str>, and instructions to be HashMap<String, Vec<String>>, then it should work I think.

use regex::Captures;
use regex::Regex;
use std::collections::HashMap;
use std::fs::File;
use std::io::{BufRead, BufReader};

fn main() {
    //read file
    let input = File::open("../input.txt").unwrap();
    let reader = BufReader::new(input);

    //ugly regex, but it does exactly what I want it to
    let re = Regex::new(r"(?:(^[[:lower:]]+|^\d+) |)(?:([[:lower:]]+|[[:upper:]]+) |)(?:([[:lower:]]+|[[:upper:]]+|\d+|) |)-> ([[:lower:]]+)$").unwrap();

    //hashmap to store the 'instructions' which is the regex groups, with the key of group 4
    let mut instructions: HashMap<String, Vec<String>> = HashMap::new();

    for line in reader.lines().into_iter() {
        let line = line.unwrap();
        println!("Line Read: {}", line);

        for caps in re.captures_iter(&line) {
            //this line is where I am having touble, with or without the '&' before line, I get a different error

            let groups: Vec<String> = caps
                .iter()
                .map(|m| match m {
                    Some(value) => value.as_str().to_string(),
                    None => "".to_string(),
                })
                .collect();

            println!("{:?}", groups); //this prints exactly what I want

            instructions.insert(groups[4].clone(), groups); //this line is the one that causes the error, because of a reference outside the loop?
        }
    }
}

Answered By - Özgür Murat Sağdıçoğlu

Answer Checked By - Cary Denson (PHPFixing Admin)