Using Validators

Once validators are defined, attach them to fields with #[koruma(...)] and derive Koruma on your data type. The derive macro generates a validate() method that runs the configured validators and returns Result<(), Errors>.

use koruma::{Koruma, KorumaAllDisplay};

#[derive(Koruma, KorumaAllDisplay)]
pub struct Item {
    #[koruma(NumberRangeValidation::<_>(min = 0, max = 100))]
    pub age: i32,

    #[koruma(StringLengthValidation(min = 1, max = 67))]
    pub name: String,

    // Fields without #[koruma(...)] are ignored by validation.
    pub internal_id: u64,
}

let item = Item {
    age: 150,
    name: "".to_string(),
    internal_id: 1,
};

match item.validate() {
    Ok(()) => println!("Item is valid"),
    Err(errors) => {
        if let Some(age_err) = errors.age().number_range_validation() {
            println!("age failed: {}", age_err);
        }
        if let Some(name_err) = errors.name().string_length_validation() {
            println!("name failed: {}", name_err);
        }
    }
}

Use TypeName::<_>(...) when the validator is generic and Rust can infer the missing type parameter. If a field has no #[koruma(...)] attribute, koruma does not validate it.

For fields with more than one validator, koruma generates accessors for each validator as well as an all() iterator when you derive KorumaAllDisplay or KorumaAllFluent. The next chapter covers that multi-validator case in more detail.