Complete errors exercises

exercises/13_error_handling/errors1.rs

@@ -9,14 +9,13 @@
 // Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
-pub fn generate_nametag_text(name: String) -> Option<String> {
+pub fn generate_nametag_text(name: String) -> Result<String, String>{
     if name.is_empty() {
         // Empty names aren't allowed.
-        None
+        Err("`name` was empty; it must be nonempty.".to_string())
     } else {
-        Some(format!("Hi! My name is {}", name))
+        Ok(format!("Hi! My name is {}", name))
     }
 }
 

exercises/13_error_handling/errors2.rs

@@ -19,16 +19,22 @@
 // Execute `rustlings hint errors2` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 use std::num::ParseIntError;
 
 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>();
+    // Same as the match expression below
+    let qty = item_quantity.parse::<i32>()?;
+    
+    // match item_quantity.parse::<i32>() {
+    //     Ok(quantity) => Ok(quantity * cost_per_item + processing_fee),
+    //     Err(e) => Err(e),
+    // }
 
-    Ok(qty * cost_per_item + processing_fee)
+    // I tried to use the if let statement but that's for Pattern matching 
+    // This is not patter matching because it's looking for conditional checks. 
 }
 
 #[cfg(test)]

exercises/13_error_handling/errors3.rs

@@ -7,11 +7,17 @@
 // Execute `rustlings hint errors3` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
+use std::error;
 
-fn main() {
+// I could have just returned the ParseIntError from the total_cost function
+// because we know the exact error that's being returned.
+
+fn main() -> Result<(), Box<dyn error::Error>>{
+    // Box <dyn error::Error> is a trait object.
+    // Meaning, you would use this when you know an error can be returned but 
+    // not necessarily what kind 
+    
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -23,6 +29,8 @@ fn main() {
         tokens -= cost;
         println!("You now have {} tokens.", tokens);
     }
+
+    Ok(())
 }
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {

exercises/13_error_handling/errors4.rs

@@ -3,7 +3,6 @@
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
@@ -17,7 +16,13 @@ enum CreationError {
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
         // Hmm... Why is this always returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+        if value > 0 {
+            Ok(PositiveNonzeroInteger(value as u64))
+        } else if value == 0 {
+            Err(CreationError::Zero)
+        } else {
+            Err(CreationError::Negative)
+        } 
     }
 }
 

exercises/13_error_handling/errors5.rs

@@ -22,14 +22,12 @@
 // Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::error;
 use std::fmt;
 use std::num::ParseIntError;
 
 // TODO: update the return type of `main()` to make this compile.
-fn main() -> Result<(), Box<dyn ???>> {
+fn main() -> Result<(), Box<dyn error::Error>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);

exercises/13_error_handling/errors6.rs

@@ -9,7 +9,6 @@
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
 
 use std::num::ParseIntError;
 
@@ -26,12 +25,15 @@ impl ParsePosNonzeroError {
     }
     // TODO: add another error conversion function here.
     // fn from_parseint...
+    fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
+        ParsePosNonzeroError::ParseInt(err)
+    }
 }
 
 fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
     // TODO: change this to return an appropriate error instead of panicking
     // when `parse()` returns an error.
-    let x: i64 = s.parse().unwrap();
+    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
     PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
 }