rustlings/solutions/23_conversions/try_from_into.rs
2024-07-02 01:26:09 +02:00

193 lines
4.9 KiB
Rust

// `TryFrom` is a simple and safe type conversion that may fail in a controlled
// way under some circumstances. Basically, this is the same as `From`. The main
// difference is that this should return a `Result` type instead of the target
// type itself. You can read more about it in the documentation:
// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
use std::convert::{TryFrom, TryInto};
#[derive(Debug, PartialEq)]
struct Color {
red: u8,
green: u8,
blue: u8,
}
// We will use this error type for the `TryFrom` conversions.
#[derive(Debug, PartialEq)]
enum IntoColorError {
// Incorrect length of slice
BadLen,
// Integer conversion error
IntConversion,
}
impl TryFrom<(i16, i16, i16)> for Color {
type Error = IntoColorError;
fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
let (Ok(red), Ok(green), Ok(blue)) = (
u8::try_from(tuple.0),
u8::try_from(tuple.1),
u8::try_from(tuple.2),
) else {
return Err(IntoColorError::IntConversion);
};
Ok(Self { red, green, blue })
}
}
impl TryFrom<[i16; 3]> for Color {
type Error = IntoColorError;
fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
// Reuse the implementation for a tuple.
Self::try_from((arr[0], arr[1], arr[2]))
}
}
impl TryFrom<&[i16]> for Color {
type Error = IntoColorError;
fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
// Check the length.
if slice.len() != 3 {
return Err(IntoColorError::BadLen);
}
// Reuse the implementation for a tuple.
Self::try_from((slice[0], slice[1], slice[2]))
}
}
fn main() {
// Using the `try_from` function.
let c1 = Color::try_from((183, 65, 14));
println!("{c1:?}");
// Since `TryFrom` is implemented for `Color`, we can use `TryInto`.
let c2: Result<Color, _> = [183, 65, 14].try_into();
println!("{c2:?}");
let v = vec![183, 65, 14];
// With slice we should use the `try_from` function
let c3 = Color::try_from(&v[..]);
println!("{c3:?}");
// or put the slice within round brackets and use `try_into`.
let c4: Result<Color, _> = (&v[..]).try_into();
println!("{c4:?}");
}
#[cfg(test)]
mod tests {
use super::*;
use IntoColorError::*;
#[test]
fn test_tuple_out_of_range_positive() {
assert_eq!(Color::try_from((256, 1000, 10000)), Err(IntConversion));
}
#[test]
fn test_tuple_out_of_range_negative() {
assert_eq!(Color::try_from((-1, -10, -256)), Err(IntConversion));
}
#[test]
fn test_tuple_sum() {
assert_eq!(Color::try_from((-1, 255, 255)), Err(IntConversion));
}
#[test]
fn test_tuple_correct() {
let c: Result<Color, _> = (183, 65, 14).try_into();
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14,
}
);
}
#[test]
fn test_array_out_of_range_positive() {
let c: Result<Color, _> = [1000, 10000, 256].try_into();
assert_eq!(c, Err(IntConversion));
}
#[test]
fn test_array_out_of_range_negative() {
let c: Result<Color, _> = [-10, -256, -1].try_into();
assert_eq!(c, Err(IntConversion));
}
#[test]
fn test_array_sum() {
let c: Result<Color, _> = [-1, 255, 255].try_into();
assert_eq!(c, Err(IntConversion));
}
#[test]
fn test_array_correct() {
let c: Result<Color, _> = [183, 65, 14].try_into();
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14
}
);
}
#[test]
fn test_slice_out_of_range_positive() {
let arr = [10000, 256, 1000];
assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
}
#[test]
fn test_slice_out_of_range_negative() {
let arr = [-256, -1, -10];
assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
}
#[test]
fn test_slice_sum() {
let arr = [-1, 255, 255];
assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
}
#[test]
fn test_slice_correct() {
let v = vec![183, 65, 14];
let c: Result<Color, _> = Color::try_from(&v[..]);
assert!(c.is_ok());
assert_eq!(
c.unwrap(),
Color {
red: 183,
green: 65,
blue: 14,
}
);
}
#[test]
fn test_slice_excess_length() {
let v = vec![0, 0, 0, 0];
assert_eq!(Color::try_from(&v[..]), Err(BadLen));
}
#[test]
fn test_slice_insufficient_length() {
let v = vec![0, 0];
assert_eq!(Color::try_from(&v[..]), Err(BadLen));
}
}