Get to Generics

exercises/error_handling/errors1.rs

@@ -6,14 +6,11 @@
 // this function to have.
 // Execute `rustlings hint errors1` for hints!
 
-// I AM NOT DONE
-
-pub fn generate_nametag_text(name: String) -> Option<String> {
+pub fn generate_nametag_text(name: String) -> Result<String, &'static str> {
     if name.len() > 0 {
-        Some(format!("Hi! My name is {}", name))
+        Ok(format!("Hi! My name is {}", name))
     } else {
-        // Empty names aren't allowed.
-        None
+        Err("`name` was empty; it must be nonempty.".into())
     }
 }
 
@@ -28,7 +25,7 @@ mod tests {
     fn generates_nametag_text_for_a_nonempty_name() {
         assert_eq!(
             generate_nametag_text("Beyoncé".into()),
-            Some("Hi! My name is Beyoncé".into())
+            Ok("Hi! My name is Beyoncé".into())
         );
     }
 

exercises/error_handling/errors2.rs

@@ -16,16 +16,15 @@
 // There are at least two ways to implement this that are both correct-- but
 // one is a lot shorter! Execute `rustlings hint errors2` for hints to both ways.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
+const PROCESSING_FEE: i32 = 1;
+const COST_PER_ITEM: i32 = 5;
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
-    let processing_fee = 1;
-    let cost_per_item = 5;
-    let qty = item_quantity.parse::<i32>();
-
-    Ok(qty * cost_per_item + processing_fee)
+    match item_quantity.parse::<i32>() {
+        Ok(qty) => Ok(qty * COST_PER_ITEM + PROCESSING_FEE),
+        error => error 
+    }
 }
 
 #[cfg(test)]

exercises/error_handling/errors3.rs

@@ -4,15 +4,18 @@
 // Why not? What should we do to fix it?
 // Execute `rustlings hint errors3` for hints!
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
-    let cost = total_cost(pretend_user_input)?;
+
+    let cost = match total_cost(pretend_user_input) {
+        Ok(cost) => cost,
+        Err(e) => return
+    };
+           
 
     if cost > tokens {
         println!("You can't afford that many!");

exercises/error_handling/errorsn.rs

@@ -17,19 +17,18 @@
 //
 // Execute `rustlings hint errorsn` for hints :)
 
-// I AM NOT DONE
-
 use std::error;
 use std::fmt;
 use std::io;
 
 // PositiveNonzeroInteger is a struct defined below the tests.
-fn read_and_validate(b: &mut dyn io::BufRead) -> Result<PositiveNonzeroInteger, ???> {
+fn read_and_validate(b: &mut dyn io::BufRead) -> Result<PositiveNonzeroInteger, Box<dyn error::Error>> {
     let mut line = String::new();
-    b.read_line(&mut line);
-    let num: i64 = line.trim().parse();
-    let answer = PositiveNonzeroInteger::new(num);
-    answer
+    b.read_line(&mut line)?;
+    let num: i64 = line.trim().parse()?;
+    let answer = PositiveNonzeroInteger::new(num)?;
+
+    Ok(answer)
 }
 
 //

exercises/move_semantics/move_semantics1.rs

@@ -1,8 +1,6 @@
 // move_semantics1.rs
 // Make me compile! Execute `rustlings hint move_semantics1` for hints :)
 
-// I AM NOT DONE
-
 fn main() {
     let vec0 = Vec::new();