How convert string to integer with suffix type like "10i32"

[mehrati]

I am trying to write a code parse string to integer

pub fn parse(s: &str) -> Option<i32>{
const NUMBERS: [&'static str; 12] = [
    "i8", "i16", "i32", "i64", "u8", "u16", "u32", "u64", "isize", "usize", "f32", "f64",
];
for int in NUMBERS.iter() {
    match s.split(int).collect::<Vec<&str>>()[0].parse::<i32>() {
        Ok(o) => {
            println!("{}", o);
            return Some(o);
        }
        Err(_) => continue,
    }
}
None

}
but problem is i force str convert to i32 not the exactly type how write generic code can infer type from str

[Yandros]

Before thinking about the technicalities of an implementation, let's first think about the signature of such a "generic/general integer" parsing function:

• input: &str;

• output: Result<_, ParseError> for some defined ParseError (depending on the amount of information the error may carry).

Now, the main question is, what should _ be ? It cannot be i32, because "32_u32" cannot (and should not) be parsed as a i32. And the same reasoning applies for other numeric types.

This is a common issue with serialization, there needs to be some form of a dynamic type. For that, there are two tools at your disposal: an enum or a trait object (abstracting over the common behavior of all these numeric types. Given that the set of numeric types is known in advance, the enum should give a more flexible (albeit cumbersome) path).

enum:

enum ParsedInt {
     I8(i8),
     U8(u8),
     // ...
     I64(i64),
     U64(u64),
}
use self::ParsedInt::*;

This way, thanks to the (dynamic) tag / name of an enum, we are now capable of unifying all these numeric types into a single type.

Now, within your parsing logic, if, for instance, you encounter "xxx_i32", you know you have to try to parse "xxx" as a i32, and on success (let's say we get x: i32), return Ok(I32(x)), etc.