生命周期

use std::collections::HashMap;

fn main() {
    let query = String::from("name=Tom&age=18&hobby=coding");
    let qp = QueryParser::from_string(query.clone());
    println!("params: {:#?}", qp);

    let qp2 = EnhancedQueryParser::from_string(&query);
    println!("params: {:#?}", qp2);

    let name = qp2.params.get("name").unwrap();
    println!("name: {}", name);
}

#[derive(Debug)]
struct QueryParser {
    query: String,
    params: HashMap<String, String>,
}

impl QueryParser {
    fn from_string(query: String) -> Self {
        // name=value&name=value
        let params: HashMap<String, String> = query
            .split("&")
            .map(|item| {
                let mut parts = item.split("=");
                let key = String::from(parts.next().expect("no key"));
                let value = String::from(parts.next().unwrap());
                (key, value)
            })
            .collect();

        Self { query, params }
    }
}

#[derive(Debug)]
struct EnhancedQueryParser<'a> {
    query: &'a str,
    params: HashMap<&'a str, &'a str>,
}

impl<'a> EnhancedQueryParser<'a> {
    fn from_string(query: &'a str) -> Self {
        let params: HashMap<&'a str, &'a str> = query
            .split("&")
            .map(|kv| {
                let mut parts = kv.split("=");
                (parts.next().unwrap(), parts.next().unwrap())
            })
            .collect();

        Self { query, params }
    }
}