Trust counts the number of occurrences of words in the file

explain

The example comes from 《 Master Rust The first 2 edition 》 [ print ] Lahore · sharma [ Fen ] VESA · Kelavita Writing Deng Shichao translate 36 page . But it could be rust The reason why language is changing , In the author rust The version is rustc 1.61.0 (fe5b13d68 2022-05-18) There are errors in the compilation of the environment , After modification, part of the code can run . Here is the modified code :

Code

use std::collections::HashMap;
use std::env;
use std::fs::File;
use std::io::prelude::BufRead;
use std::io::BufReader;

//  Define a Tuple Struct（ Tuple structure , The characteristic of tuple structure is that fields only have types , There is no name ）
#[derive(Debug)]
struct WordCounter(HashMap<String,u64>);

impl WordCounter{
    
    fn new() -> WordCounter{
    
        //  Create tuple structure WordCounter Example , The first element of a tuple is HashMap Type instance 
        WordCounter(HashMap::new())
    }

    // &mut self As the first parameter , Then this method provides variable access to type instances 
    fn increment(&mut self, word:&str){
    
        let key = word.to_string();
        // self.0 Represents getting tuple structure WordCounter The first element of , namely HashMap Example 
        let count = self.0.entry(key).or_insert(0);
        //  The number of words plus 1
        *count += 1;
    }

    fn display(self){
    
        for (key,value) in self.0.iter() {
    
            println!(" word :{} There is {} Time ", key, value);
        }
    }
}
fn main() {
    
    let arguments: Vec<String> = env::args().collect();
    //  I need it here &arguments
    let filename = &arguments[1];
    println!("Processing file:{}",filename);
    let file = File::open(filename).expect("Could not open file");
    let reader = BufReader::new(file);
    let mut word_counter = WordCounter::new();
    for line in reader.lines() {
    
        let line = line.expect("Could not read line");
        //  Each line of text is separated by spaces 
        let words = line.split(" ");
        for word in words {
    
            if word == ""{
    
                continue
            } else {
    
                word_counter.increment(word);
            }
        }

    }

    word_counter.display();
}

Running effect