Expand description


use serde::Deserialize;

// A trait that the Validate derive will impl
use validator::{Validate, ValidationError};

#[derive(Debug, Validate, Deserialize)]
struct SignupData {
    mail: String,
    phone: String,
    site: String,
    #[validate(length(min = 1), custom = "validate_unique_username")]
    #[serde(rename = "firstName")]
    first_name: String,
    #[validate(range(min = 18, max = 20))]
    age: u32,

fn validate_unique_username(username: &str) -> Result<(), ValidationError> {
    if username == "xXxShad0wxXx" {
        // the value of the username will automatically be added later
        return Err(ValidationError::new("terrible_username"));


match signup_data.validate() {
  Ok(_) => (),
  Err(e) => return e;

Available Validations:

credit_card(Requires the feature card to be enabled)
phone(Requires the feature phone to be enabled)
non_control_character(Required the feature unic to be enabled)
nested(Uses the validation of the field type it self)

Checkout the project README of an in-depth usage description with examples.


Add the validator to the dependencies in the Cargo.toml file.

validator = { version = "0.12", features = ["derive"] }




Trait to implement if one wants to make the contains validator work for more types

Trait to implement if one wants to make the length validator work for more types

This is the original trait that was implemented by deriving Validate. It will still be implemented for struct validations that don’t take custom arguments. The call is being forwarded to the ValidateArgs<'v_a> trait.

This trait will be implemented by deriving Validate. This implementation can take one argument and pass this on to custom validators. The default Args type will be () if there is no custom validation with defined arguments.


Validates whether the value contains the needle The value needs to implement the Contains trait, which is implement on String, str and Hashmap by default.

Validates whether the given string is an email based on the HTML5 spec. RFC 5322 is not practical in most circumstances and allows email addresses that are unfamiliar to most users.

Validates whether the given string is an IP

Validates whether the given string is an IP V4

Validates whether the given string is an IP V6

Validates the length of the value given. If the validator has equal set, it will ignore any min and max value.

Validates that the 2 given fields match. Both fields are optionals

Validates that the given value is inside the defined range. The max and min parameters are optional and will only be validated if they are not None

Validates whether the given Option is Some

Validates whether the string given is a url