How to convert fields during deserialization using Serde?

Question

I use Serde to deserialize an XML file with a hex value 0x400as a string, and I need to convert it to a value 1024like u32.

Do I need to implement the trait Visitorso that I separate 0x and then decrypt 400 from base 16 to base 10? If so, how do I do this so that deserialization for integers of base 10 remains intact?

Answer 1

Attribute deserialize_with

Serde deserialize_with . :

use serde::{de::Error, Deserialize, Deserializer}; // 1.0.94
use serde_json; // 1.0.40

#[derive(Debug, Deserialize)]
struct EtheriumTransaction {
    #[serde(deserialize_with = "from_hex")]
    account: u64, // hex
    amount: u64, // decimal
}

fn from_hex<'de, D>(deserializer: D) -> Result<u64, D::Error>
where
    D: Deserializer<'de>,
{
    let s: &str = Deserialize::deserialize(deserializer)?;
    // do better hex decoding than this
    u64::from_str_radix(&s[2..], 16).map_err(D::Error::custom)
}

fn main() {
    let raw = r#"{"account": "0xDEADBEEF", "amount": 100}"#;
    let transaction: EtheriumTransaction =
        serde_json::from_str(raw).expect("Couldn't derserialize");
    assert_eq!(transaction.amount, 100);
    assert_eq!(transaction.account, 0xDEAD_BEEF);
}

, Serde . (let s: &str = Deserialize::deserialize(deserializer)?). , , Deserialize , Deserialize.

serde::Deserialize

, , :

#[derive(Debug, Deserialize)]
struct EtheriumTransaction {
    account: Account, // hex
    amount: u64,      // decimal
}

#[derive(Debug, PartialEq)]
struct Account(u64);

impl<'de> Deserialize<'de> for Account {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let s: &str = Deserialize::deserialize(deserializer)?;
        // do better hex decoding than this
        u64::from_str_radix(&s[2..], 16)
            .map(Account)
            .map_err(D::Error::custom)
    }
}

, "" , .

:

• Serde?