rustlings/exercises/conversions/try_from_into.rs

// try_from_into.rs
// 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 at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for a hint.

use std::convert::{TryFrom, TryInto};

#[derive(Debug, PartialEq)]
struct Color {
    red: u8,
    green: u8,
    blue: u8,
}

// We will use this error type for these `TryFrom` conversions.
#[derive(Debug, PartialEq)]
enum IntoColorError {
    // Incorrect length of slice
    BadLen,
    // Integer conversion error
    IntConversion,
}

// Your task is to complete this implementation
// and return an Ok result of inner type Color.
// You need to create an implementation for a tuple of three integers,
// an array of three integers, and a slice of integers.
//
// Note that the implementation for tuple and array will be checked at compile time,
// but the slice implementation needs to check the slice length!
// Also note that correct RGB color values must be integers in the 0..=255 range.

// Tuple implementation
impl TryFrom<(i16, i16, i16)> for Color {
    type Error = IntoColorError;
    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
        let x: u8 = tuple
            .0
            .try_into()
            .map_err(|_| IntoColorError::IntConversion)?;
        let y: u8 = tuple
            .1
            .try_into()
            .map_err(|_| IntoColorError::IntConversion)?;
        let z: u8 = tuple
            .2
            .try_into()
            .map_err(|_| IntoColorError::IntConversion)?;

        Ok(Color {
            red: x,
            green: y,
            blue: z,
        })
    }
}

// Array implementation
impl TryFrom<[i16; 3]> for Color {
    type Error = IntoColorError;
    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
        let mut a: [u8; 3] = [0, 0, 0];
        // arr.into_iter().enumerate().map(|(i, x)| {
        //     let t: u8 = match x.try_into() {
        //         Ok(i) => i,
        //         Err(err) => {
        //             return Err(IntoColorError::IntConversion);
        //         }
        //     };
        // });
        for (i, x) in arr.into_iter().enumerate() {
            let tmp: u8 = match x.to_owned().try_into() {
                Ok(i) => i,
                Err(err) => {
                    return Err(IntoColorError::IntConversion);
                }
            };
            // let tmp: u8 = x.try_into():IntoColorError::IntConversion;
            a[i] = tmp
        }
        Ok(Color {
            red: a[0],
            green: a[1],
            blue: a[2],
        })
    }
}

// Slice implementation
impl TryFrom<&[i16]> for Color {
    type Error = IntoColorError;
    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
        if slice.len() != 3 {
            return Err(IntoColorError::BadLen);
        }
        let mut a: [u8; 3] = [0, 0, 0];
        // arr.iter().enumerate().map(|(i, x)| {
        //     x = x.try_into()
        // })
        for (i, x) in slice.into_iter().enumerate() {
            let tmp: u8 = match x.to_owned().try_into() {
                Ok(i) => i,
                Err(err) => {
                    return Err(IntoColorError::IntConversion);
                }
            };
            a[i] = tmp
        }
        Ok(Color {
            red: a[0],
            green: a[1],
            blue: a[2],
        })
    }
}

fn main() {
    // Use the `try_from` function
    let c1 = Color::try_from((183, 65, 14));
    println!("{:?}", c1);

    // Since TryFrom is implemented for Color, we should be able to use TryInto
    let c2: Result<Color, _> = [183, 65, 14].try_into();
    println!("{:?}", c2);

    let v = vec![183, 65, 14];
    // With slice we should use `try_from` function
    let c3 = Color::try_from(&v[..]);
    println!("{:?}", c3);
    // or take slice within round brackets and use TryInto
    let c4: Result<Color, _> = (&v[..]).try_into();
    println!("{:?}", c4);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_tuple_out_of_range_positive() {
        assert_eq!(
            Color::try_from((256, 1000, 10000)),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_tuple_out_of_range_negative() {
        assert_eq!(
            Color::try_from((-1, -10, -256)),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_tuple_sum() {
        assert_eq!(
            Color::try_from((-1, 255, 255)),
            Err(IntoColorError::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(IntoColorError::IntConversion));
    }
    #[test]
    fn test_array_out_of_range_negative() {
        let c: Result<Color, _> = [-10, -256, -1].try_into();
        assert_eq!(c, Err(IntoColorError::IntConversion));
    }
    #[test]
    fn test_array_sum() {
        let c: Result<Color, _> = [-1, 255, 255].try_into();
        assert_eq!(c, Err(IntoColorError::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(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_slice_out_of_range_negative() {
        let arr = [-256, -1, -10];
        assert_eq!(
            Color::try_from(&arr[..]),
            Err(IntoColorError::IntConversion)
        );
    }
    #[test]
    fn test_slice_sum() {
        let arr = [-1, 255, 255];
        assert_eq!(
            Color::try_from(&arr[..]),
            Err(IntoColorError::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(IntoColorError::BadLen));
    }
    #[test]
    fn test_slice_insufficient_length() {
        let v = vec![0, 0];
        assert_eq!(Color::try_from(&v[..]), Err(IntoColorError::BadLen));
    }
}