feat: FromStr

README.md

@@ -4,6 +4,8 @@ This repository offers some Rust snippets that might be useful when studying the
 
 - [vec_any](src/vec_any.rs) Collect trait objects in a vector and use downcast_ref to access the concrete type instances of the items
 - [mutate_in_closure](src/mutate_in_closure.rs) Mutate a value in a closure without copy and clone
+- [from_str](src/from_str.rs) Thou shall not implement From\<str'> but instead implement the FromStr trait
+- [graphemes](src/graphemes.rs) Trim an unicode string to a maximum length with
 
 ## Run the snippets
 

src/from_str.rs

@@ -0,0 +1,28 @@
+use std::{num::ParseFloatError, str::FromStr};
+
+pub struct Angle {
+  pub radians: f64,
+}
+
+// Never implement From<&str> or From<String> as FromStr is made for this
+impl FromStr for Angle {
+  type Err = ParseFloatError;
+
+  fn from_str(s: &str) -> Result<Self, Self::Err> {
+    let radians = s.parse::<f64>()?;
+    Ok(Angle { radians })
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn test_from_str() {
+    match "1.57".parse::<Angle>() {
+      Ok(angle) => assert_eq!(angle.radians, 1.57),
+      Err(_) => panic!("Could not parse angle"),
+    }
+  }
+}

src/graphemes.rs

@@ -1,8 +1,6 @@
-#![allow(dead_code)]
-
 use unicode_segmentation::UnicodeSegmentation;
 
-trait Trim {
+pub trait Trim {
   fn trim_count(&self, count: usize) -> String;
 }
 

src/lib.rs

@@ -1,3 +1,4 @@
+pub mod from_str;
 pub mod graphemes;
 pub mod mutate_in_closure;
 pub mod vec_any;