/*
Import Traits
*/
use std::error::Error;
use std::convert::TryFrom;
use std::convert::TryInto;
/*
Declare array of seasons
*/
const array_of_seasons:[i32;5] = [
1
,2
,3
,4
,5
];
/*
Declare enum Season
print using debug symbols
------------------------
#[derive(Debug)]
compare enum values against other enum values
---------------------------------------------
#[derive(PartialEq, Eq)]
*/
#[derive(Debug)]
#[derive(PartialEq, Eq)]
enum Season
{
Winter = 1
, Spring = 2
, Summer = 3
, Autumn = 4
}
/*
Attempt to convert u16 to Enum Season
*/
/*
How do I match enum values with an integer?
https://stackoverflow.com/questions/28028854/how-do-i-match-enum-values-with-an-integer?rq=1
*/
impl TryFrom<i32> for Season
{
type Error = ();
fn try_from(v: i32) -> Result<Self, Self::Error>
{
match v
{
x if x == Season::Winter as i32 => Ok(Season::Winter),
x if x == Season::Spring as i32 => Ok(Season::Spring),
x if x == Season::Summer as i32 => Ok(Season::Summer),
x if x == Season::Autumn as i32 => Ok(Season::Autumn),
_ => Err(()),
}
}
}
/*
How do I match enum values with an integer?
https://stackoverflow.com/questions/58393250/returning-error-message-to-function-expecting-boxdyn-error
*/
fn fetchSeason
(
value:i32
) -> Result<Season, Box<dyn Error>>
{
//declare type Error
type Error = ();
//declare result as season
let result:Season;
if value == Season::Winter as i32
{
result = Season::Winter;
}
else if value == Season::Spring as i32
{
result = Season::Spring;
}
else if value == Season::Summer as i32
{
result = Season::Summer;
}
else if value == Season::Autumn as i32
{
result = Season::Autumn;
}
else
{
//raise informative error
//convert string to err type
return Err
(
"Error Unexpected argument (value)".into()
);
}
//return OK and season (as result)
return Ok(result);
}
fn getArrayElementUsingEnumValuesEqualityCheck()
{
/*
Declare array pointer
*/
let mut i:u16;
let mut array_element_value:i32;
/*
Declare function return variable
*/
let mut season_context:Result<Season, Box<dyn Error>>;
println!("Function:- getArrayElementUsingEnumValuesEqualityCheck");
println!("");
/*
Iterate array
*/
i =0;
for array_element in array_of_seasons.iter()
{
//move array pointer
i = i + 1;
//get value that pointer is pointing to
array_element_value = *array_element;
//get array element as enum
season_context = fetchSeason
(
array_element_value
);
//print array element to console
println!
(
"\tElement {} is {} (int) | {:?} ( enum )"
, i
, array_element
, season_context
);
}
println!("");
println!("");
}
fn getArrayElementsUsingTryInto()
{
/*
Declare array pointer
*/
let mut i:u16;
/*
Declare function return variable
*/
let mut season_context:Result<Season, ()>;
println!("Function:- getArrayElementsUsingTryInto");
println!("");
/*
Iterate array
*/
i =0;
for array_element in array_of_seasons.iter()
{
//move array pointer
i = i + 1;
//get value that pointer is pointing to
let array_element_value:i32 = *array_element;
//try to convert int into enum value
//using tryinto
season_context
= <i32 as TryInto<Season>>::try_into
(
array_element_value
);
//print array element to console
println!
(
"\tElement {} is {} (int) | {:?} ( enum )"
, i
, array_element
, season_context
);
}
println!("");
println!("");
}
fn getArrayElementsUsingTryFrom()
{
/*
Declare array pointer
*/
let mut i:u16;
/*
declare value of array element
*/
let mut array_element_value:i32;
/*
Declare function return variable
*/
let mut season_context:Result<Season, ()>;
println!("Function:- getArrayElementsUsingTryFrom");
println!("");
/*
Iterate array
*/
i =0;
for array_element in array_of_seasons.iter()
{
//move array pointer
i = i + 1;
//get value that pointer is pointing to
array_element_value = *array_element;
//attempt to get season enum from int
//use try_from
//implemented earlier
season_context = Season::try_from
(
array_element_value
);
//print array element to console
println!
(
"\tElement {} is {} (int) | {:?} ( enum )"
, i
, array_element
, season_context
);
}
println!("");
println!("");
}
fn main()
{
getArrayElementUsingEnumValuesEqualityCheck();
getArrayElementsUsingTryInto();
getArrayElementsUsingTryFrom();
}
