错误处理 测试 特性

rust/rustlings/exercises/error_handling/errors1.rs

@@ -5,14 +5,12 @@
 // construct to `Option` that can be used to express error conditions. Let's use it!
 // 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
+        Result::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))
     }
 }
 

rust/rustlings/exercises/error_handling/errors2.rs

@@ -17,16 +17,22 @@
 // one is a lot shorter!
 // 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>()?; // 简短的写法是使用?
+
+    // 冗长的写法;  前一种写法就很类似Maybe Monad了吧
     let qty = item_quantity.parse::<i32>();
+    if let Ok(q) = qty {
+        Ok(q * cost_per_item + processing_fee)
+    } else {
+        qty
+    }
 
-    Ok(qty * cost_per_item + processing_fee)
+    // Ok(qty * cost_per_item + processing_fee)
 }
 
 #[cfg(test)]

rust/rustlings/exercises/error_handling/errors3.rs

@@ -4,11 +4,10 @@
 // Why not? What should we do to fix it?
 // Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
-fn main() {
+fn main() -> Result<(), ParseIntError>{
+
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -20,6 +19,8 @@ fn main() {
         tokens -= cost;
         println!("You now have {} tokens.", tokens);
     }
+
+    Ok(())
 }
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {

rust/rustlings/exercises/error_handling/errors4.rs

@@ -1,8 +1,6 @@
 // errors4.rs
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
 
@@ -14,8 +12,13 @@ enum CreationError {
 
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        // Hmm...? Why is this only returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+        if value > 0 {
+            Ok(PositiveNonzeroInteger(value as u64))
+        } else if (value < 0) {
+            Err(CreationError::Negative)
+        } else {
+            Err(CreationError::Zero)
+        }
     }
 }
 

rust/rustlings/exercises/error_handling/errors5.rs

@@ -14,14 +14,12 @@
 
 // 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)?);

rust/rustlings/exercises/error_handling/errors6.rs

@@ -8,33 +8,34 @@
 
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 // This is a custom error type that we will be using in `parse_pos_nonzero()`.
 #[derive(PartialEq, Debug)]
 enum ParsePosNonzeroError {
     Creation(CreationError),
-    ParseInt(ParseIntError)
+    ParseInt(ParseIntError),
 }
 
 impl ParsePosNonzeroError {
     fn from_creation(err: CreationError) -> ParsePosNonzeroError {
         ParsePosNonzeroError::Creation(err)
     }
     // 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>
-{
+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();
-    PositiveNonzeroInteger::new(x)
-        .map_err(ParsePosNonzeroError::from_creation)
+    let x = s.parse();
+    match x {
+        Ok(x) => PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation),
+        // 不知道这种写法是否为最优写法
+        Err(x) => Err(ParsePosNonzeroError::from_parseint(x))
+    }
 }
 
 // Don't change anything below this line.
@@ -53,7 +54,7 @@ impl PositiveNonzeroInteger {
         match value {
             x if x < 0 => Err(CreationError::Negative),
             x if x == 0 => Err(CreationError::Zero),
-            x => Ok(PositiveNonzeroInteger(x as u64))
+            x => Ok(PositiveNonzeroInteger(x as u64)),
         }
     }
 }

rust/rustlings/exercises/generics/generics1.rs

@@ -3,9 +3,7 @@
 
 // Execute `rustlings hint generics1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    let mut shopping_list: Vec<?> = Vec::new();
+    let mut shopping_list: Vec<&str> = Vec::new();
     shopping_list.push("milk");
 }

rust/rustlings/exercises/generics/generics2.rs

@@ -3,14 +3,13 @@
 
 // Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
-struct Wrapper {
-    value: u32,
+struct Wrapper<T>{
+    value: T,
 }
 
-impl Wrapper {
-    pub fn new(value: u32) -> Self {
+// 语法: 这里需要写两个泛型参数
+impl<T> Wrapper<T> {
+    pub fn new(value: T) -> Self {
         Wrapper { value }
     }
 }

rust/rustlings/exercises/lifetimes/lifetimes1.rs

@@ -9,7 +9,7 @@
 
 // I AM NOT DONE
 
-fn longest(x: &str, y: &str) -> &str {
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x
     } else {

rust/rustlings/exercises/options/options1.rs

@@ -1,8 +1,6 @@
 // options1.rs
 // Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 // you can modify anything EXCEPT for this function's signature
 fn print_number(maybe_number: Option<u16>) {
     println!("printing: {}", maybe_number.unwrap());
@@ -14,7 +12,11 @@ fn print_number(maybe_number: Option<u16>) {
 // TODO: Return an Option!
 fn maybe_icecream(time_of_day: u16) -> Option<u16> {
     // We use the 24-hour system here, so 10PM is a value of 22
-    ???
+    if time_of_day < 22 {
+        Some(5)
+    } else {
+        None
+    }
 }
 
 #[cfg(test)]
@@ -32,6 +34,7 @@ mod tests {
     fn raw_value() {
         // TODO: Fix this test. How do you get at the value contained in the Option?
         let icecreams = maybe_icecream(12);
+        let icecreams = icecreams.unwrap();
         assert_eq!(icecreams, 5);
     }
 }

rust/rustlings/exercises/options/options2.rs

@@ -1,13 +1,11 @@
 // options2.rs
 // Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     let optional_word = Some(String::from("rustlings"));
     // TODO: Make this an if let statement whose value is "Some" type
-    word = optional_word {
-        println!("The word is: {}", word);
+    if let word = optional_word {
+        println!("The word is: {}", word.unwrap());
     } else {
         println!("The optional word doesn't contain anything");
     }
@@ -17,9 +15,12 @@ fn main() {
         optional_integers_vec.push(Some(x));
     }
 
-    // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
+    // TODO: make this a while let statement - remember that vector.pop also
+    // adds another layer of Option<T>
     // You can stack `Option<T>`'s into while let and if let
-    integer = optional_integers_vec.pop() {
-        println!("current value: {}", integer);
+    while let Some(integer) = optional_integers_vec.pop() {
+        if let i = integer {
+            println!("current value: {}", i.unwrap());
+        }
     }
 }

rust/rustlings/exercises/options/options3.rs

@@ -1,18 +1,18 @@
 // options3.rs
 // Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 struct Point {
     x: i32,
     y: i32,
 }
 
 fn main() {
+    // 推测自然是只有堆上对象才需要如此处理
     let y: Option<Point> = Some(Point { x: 100, y: 200 });
 
     match y {
-        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
+        // 使用ref表示仅借用,不移动; 不影响一个值是否匹配,只影响匹配方式: 借用还是move
+        Some(ref p) => println!("Co-ordinates are {},{} ", p.x, p.y),
         _ => println!("no match"),
     }
     y; // Fix without deleting this line.

rust/rustlings/exercises/quiz3.rs

@@ -14,15 +14,14 @@
 
 // Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
-pub struct ReportCard {
-    pub grade: f32,
+pub struct ReportCard <T: std::fmt::Display>{
+    pub grade: T,
     pub student_name: String,
     pub student_age: u8,
 }
 
-impl ReportCard {
+// 语法原来如此
+impl <T: std::fmt::Display> ReportCard <T>{
     pub fn print(&self) -> String {
         format!("{} ({}) - achieved a grade of {}",
             &self.student_name, &self.student_age, &self.grade)
@@ -50,7 +49,7 @@ mod tests {
     fn generate_alphabetic_report_card() {
         // TODO: Make sure to change the grade here after you finish the exercise.
         let report_card = ReportCard {
-            grade: 2.1,
+            grade: "A+".to_string(),
             student_name: "Gary Plotter".to_string(),
             student_age: 11,
         };

rust/rustlings/exercises/tests/tests1.rs

@@ -7,12 +7,10 @@
 // pass! Make the test fail!
 // Execute `rustlings hint tests1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[cfg(test)]
 mod tests {
     #[test]
     fn you_can_assert() {
-        assert!();
+        assert!(true);
     }
 }

rust/rustlings/exercises/tests/tests2.rs

@@ -3,12 +3,10 @@
 // pass! Make the test fail!
 // Execute `rustlings hint tests2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[cfg(test)]
 mod tests {
     #[test]
     fn you_can_assert_eq() {
-        assert_eq!();
+        assert_eq!(true, true);
     }
 }

rust/rustlings/exercises/tests/tests3.rs

@@ -4,8 +4,6 @@
 // we expect to get when we call `is_even(5)`.
 // Execute `rustlings hint tests3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 pub fn is_even(num: i32) -> bool {
     num % 2 == 0
 }
@@ -16,11 +14,11 @@ mod tests {
 
     #[test]
     fn is_true_when_even() {
-        assert!();
+        assert!(is_even(2) == true);
     }
 
     #[test]
     fn is_false_when_odd() {
-        assert!();
+        assert!(is_even(3) == false);
     }
 }

rust/rustlings/exercises/traits/traits1.rs

@@ -9,14 +9,15 @@
 // implementing this trait.
 // Execute `rustlings hint traits1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 trait AppendBar {
     fn append_bar(self) -> Self;
 }
 
 impl AppendBar for String {
     //Add your code here
+    fn append_bar(self) -> Self {
+        self + "Bar"
+    }
 }
 
 fn main() {