From 050a23ce6763fedf0906cd1c04b76888aae12f7d Mon Sep 17 00:00:00 2001
From: mo8it <mo8it@proton.me>
Date: Wed, 26 Jun 2024 15:36:14 +0200
Subject: [PATCH] errors2 solution
---
exercises/13_error_handling/errors2.rs | 19 +++++----
rustlings-macros/info.toml | 7 ++--
solutions/13_error_handling/errors2.rs | 58 +++++++++++++++++++++++++-
3 files changed, 71 insertions(+), 13 deletions(-)
diff --git a/exercises/13_error_handling/errors2.rs b/exercises/13_error_handling/errors2.rs
index 345a0eef..e50a9299 100644
--- a/exercises/13_error_handling/errors2.rs
+++ b/exercises/13_error_handling/errors2.rs
@@ -2,16 +2,16 @@
// 5 tokens, and whenever you purchase items there is a processing fee of 1
// token. A player of the game will type in how many items they want to buy, and
// the `total_cost` function will calculate the total cost of the items. Since
-// the player typed in the quantity, though, we get it as a string-- and they
-// might have typed anything, not just numbers!
+// the player typed in the quantity, we get it as a string. They might have
+// typed anything, not just numbers!
//
// Right now, this function isn't handling the error case at all (and isn't
-// handling the success case properly either). What we want to do is: if we call
+// handling the success case properly either). What we want to do is: If we call
// the `total_cost` function on a string that is not a number, that function
-// will return a `ParseIntError`, and in that case, we want to immediately
-// return that error from our function and not try to multiply and add.
+// will return a `ParseIntError`. In that case, we want to immediately return
+// that error from our function and not try to multiply and add.
//
-// There are at least two ways to implement this that are both correct-- but one
+// There are at least two ways to implement this that are both correct. But one
// is a lot shorter!
use std::num::ParseIntError;
@@ -19,6 +19,8 @@ use std::num::ParseIntError;
fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
let processing_fee = 1;
let cost_per_item = 5;
+
+ // TODO: Handle the error case as described above.
let qty = item_quantity.parse::<i32>();
Ok(qty * cost_per_item + processing_fee)
@@ -31,6 +33,7 @@ fn main() {
#[cfg(test)]
mod tests {
use super::*;
+ use std::num::IntErrorKind;
#[test]
fn item_quantity_is_a_valid_number() {
@@ -40,8 +43,8 @@ mod tests {
#[test]
fn item_quantity_is_an_invalid_number() {
assert_eq!(
- total_cost("beep boop").unwrap_err().to_string(),
- "invalid digit found in string"
+ total_cost("beep boop").unwrap_err().kind(),
+ &IntErrorKind::InvalidDigit,
);
}
}
diff --git a/rustlings-macros/info.toml b/rustlings-macros/info.toml
index 3d8da58f..2a4a24ea 100644
--- a/rustlings-macros/info.toml
+++ b/rustlings-macros/info.toml
@@ -660,12 +660,11 @@ One way to handle this is using a `match` statement on
`item_quantity.parse::<i32>()` where the cases are `Ok(something)` and
`Err(something)`.
-This pattern is very common in Rust, though, so there's a `?` operator that
+This pattern is very common in Rust, though, so there's the `?` operator that
does pretty much what you would make that match statement do for you!
-Take a look at this section of the 'Error Handling' chapter:
-https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
-and give it a try!"""
+Take a look at this section of the "Error Handling" chapter:
+https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator"""
[[exercises]]
name = "errors3"
diff --git a/solutions/13_error_handling/errors2.rs b/solutions/13_error_handling/errors2.rs
index 4e181989..de7c32b5 100644
--- a/solutions/13_error_handling/errors2.rs
+++ b/solutions/13_error_handling/errors2.rs
@@ -1 +1,57 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Say we're writing a game where you can buy items with tokens. All items cost
+// 5 tokens, and whenever you purchase items there is a processing fee of 1
+// token. A player of the game will type in how many items they want to buy, and
+// the `total_cost` function will calculate the total cost of the items. Since
+// the player typed in the quantity, we get it as a string. They might have
+// typed anything, not just numbers!
+//
+// Right now, this function isn't handling the error case at all (and isn't
+// handling the success case properly either). What we want to do is: If we call
+// the `total_cost` function on a string that is not a number, that function
+// will return a `ParseIntError`. In that case, we want to immediately return
+// that error from our function and not try to multiply and add.
+//
+// There are at least two ways to implement this that are both correct. But one
+// is a lot shorter!
+
+use std::num::ParseIntError;
+
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+ let processing_fee = 1;
+ let cost_per_item = 5;
+
+ // Added `?` to propagate the error.
+ let qty = item_quantity.parse::<i32>()?;
+ // ^ added
+
+ // Equivalent to this verbose version:
+ let qty = match item_quantity.parse::<i32>() {
+ Ok(v) => v,
+ Err(e) => return Err(e),
+ };
+
+ Ok(qty * cost_per_item + processing_fee)
+}
+
+fn main() {
+ // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use std::num::IntErrorKind;
+
+ #[test]
+ fn item_quantity_is_a_valid_number() {
+ assert_eq!(total_cost("34"), Ok(171));
+ }
+
+ #[test]
+ fn item_quantity_is_an_invalid_number() {
+ assert_eq!(
+ total_cost("beep boop").unwrap_err().kind(),
+ &IntErrorKind::InvalidDigit,
+ );
+ }
+}