refactored code in minigrep to properly use iterators.

the_book/minigrep/src/lib.rs

@@ -1,5 +1,5 @@
-use std::error::Error;
 use std::env;
+use std::error::Error;
 use std::fs;
 
 pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
@@ -22,40 +22,39 @@ pub struct Config {
 }
 
 impl Config {
-    pub fn new(args: &[String]) -> Result<Config, &'static str> {
-        if args.len() < 3 {
-            return Err("Not enough arguments");
-        }
-        let query = args[1].clone();
-        let filename = args[2].clone();
+    pub fn new(mut args: impl Iterator<Item = String>) -> Result<Config, &'static str> {
+        args.next();
+
+        let query = match args.next() {
+            Some(arg) => arg,
+            None => return Err("Didn't get a query string."),
+        };
+        let filename = match args.next() {
+            Some(arg) => arg,
+            None => return Err("Didn't get a file name."),
+        };
+
         let ignore_case = env::var("IGNORE_CASE").is_ok();
-        Ok(Config { query, filename, ignore_case })
+        Ok(Config {
+            query,
+            filename,
+            ignore_case,
+        })
     }
 }
 
 pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
-    let mut results = Vec::new();
-
-    for line in contents.lines() {
-        if line.contains(query) {
-            results.push(line);
-        }
-    }
-
-    results
+    contents
+        .lines()
+        .filter(|line| line.contains(query))
+        .collect()
 }
 
 pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
-    let query = query.to_lowercase();
-    let mut results = Vec::new();
-
-    for line in contents.lines() {
-        if line.to_lowercase().contains(&query) {
-            results.push(line);
-        }
-    }
-
-    results
+    contents
+        .lines()
+        .filter(|line| line.to_lowercase().contains(&query.to_lowercase()))
+        .collect()
 }
 
 #[cfg(test)]

the_book/minigrep/src/main.rs

@@ -4,9 +4,7 @@ use std::process;
 use minigrep::Config;
 
 fn main() {
-    let args: Vec<String> = env::args().collect();
-
-    let config = Config::new(&args).unwrap_or_else(|err| {
+    let config = Config::new(env::args()).unwrap_or_else(|err| {
         eprintln!("Problem parsing arguments: {}", err);
         process::exit(1);
     });