Some error handling included

city-pop/src/main.rs

@@ -26,7 +26,7 @@ struct Row {
 
 struct PopulationCount {
     city: String,
-    country: String
+    country: String,
     // This is no longer an `Option` because values of this type are only
     // constructed if they have a population count.
     count: u64,
@@ -36,6 +36,26 @@ fn print_usage(program: &str, opts: Options) {
     println!("{}", opts.usage(&format!("Usage: {} [options] <data-path> <city>",program)));
 }
 
+fn search<P: AsRef<path::Path>>(file_path: P, city: &str) -> Vec<PopulationCount> {
+    let mut found = vec![];
+    let file = fs::File::open(file_path).unwrap();
+    let mut rdr = csv::Reader::from_reader(file);
+    for row in rdr.decode::<Row>() {
+        let row = row.unwrap();
+        match row.population {
+            None => { }
+            Some(count) => if row.city == city {
+                found.push(PopulationCount {
+                    city: row.city,
+                    country: row.country,
+                    count: count,
+                });
+            },
+        }
+    }
+    found
+}
+
 fn main() {
     let args: Vec<String> = env::args().collect();
     let program = args[0].clone();
@@ -56,16 +76,8 @@ fn main() {
     let data_path = path::Path::new(&data_file);
     let city = args[2].clone();
 
-    let file = fs::File::open(data_path).unwrap();
-    let mut rdr = csv::Reader::from_reader(file);
-
-    for row in rdr.decode::<Row>() {
-        let row = row.unwrap();
-
-        if row.city == city {
-            println!("{}, {}: {:?}",
-                     row.city, row.country,
-                     row.population.expect("population count"));
-        }
+    for pop in search(&data_path, &city) {
+        println!("{}, {}: {:?}",pop.city, pop.country, pop.count);
     }
+
 }