Struct Lenient

pub struct Lenient<T>(/* private fields */);

A form guard for parsing form types leniently.

This type implements the FromForm trait and thus can be used as a generic parameter to the Form data guard: Form<Lenient<T>>, where T implements FromForm. Unlike using Form directly, this type uses a lenient parsing strategy.

Lenient Parsing

A Lenient<T> will parse successfully from an incoming form even if the form contains extra or missing fields. If fields are missing, the form field type’s default will be used, if there is one. Extra fields are ignored; only the first is parsed and validated. This is the default strategy for Form.

Usage

Lenient<T> implements FromForm as long as T implements FromForm. As such, Form<Lenient<T>> is a data guard.

Note that Form<T> already parses leniently, so a Form<Lenient<T>> is redundant and equal to Form<T>. Lenient, however, can be used to make otherwise strict parses lenient, for example, in Option<Lenient<T>>:

use rocket::form::Lenient;

#[derive(FromForm)]
struct UserInput {
    // Parses as `Some(false)` when `lenient_inner_option` isn't present.
    // Without `Lenient`, this would otherwise parse as `None`.
    lenient_inner_option: Option<Lenient<bool>>,
}

Implementations

impl<T> Lenient<T>

pub fn into_inner(self) -> T

Consumes self and returns the inner value.

Note that since Lenient implements Deref and DerefMut with target T, reading and writing an inner value can be accomplished transparently.

Example

use rocket::form::{Form, Lenient};

#[derive(FromForm)]
struct MyForm {
    field: String,
}

#[post("/submit", data = "<form>")]
fn submit(form: Form<Lenient<MyForm>>) -> String {
    // We can read or mutate a value transparently:
    let field: &str = &form.field;

    // To gain ownership, however, use `into_inner()`:
    form.into_inner().into_inner().field
}

Trait Implementations

impl<T: Debug> Debug for Lenient<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Deref for Lenient<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T> DerefMut for Lenient<T>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T> From<T> for Lenient<T>

fn from(val: T) -> Lenient<T>

Converts to this type from the input type.

impl<'v, T: FromForm<'v>> FromForm<'v> for Lenient<T>

type Context = <T as FromForm<'v>>::Context

The form guard’s parsing context.

fn init(_: Options) -> Self::Context

Initializes and returns the parsing context for Self.

fn push_value(ctxt: &mut Self::Context, field: ValueField<'v>)

Processes the value field field.

fn push_data<'life0, 'life1, 'async_trait>( ctxt: &'life0 mut Self::Context, field: DataField<'v, 'life1>, ) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>

where Self: 'async_trait, 'v: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

Processes the data field field.

fn finalize(this: Self::Context) -> Result<'v, Self>

Finalizes parsing. Returns the parsed value when successful or collection of Errors otherwise.

fn push_error(_ctxt: &mut Self::Context, _error: Error<'r>)

Processes the external form or field error _error.

fn default(opts: Options) -> Option<Self>

Returns a default value, if any, to use when a value is desired and parsing fails.

impl<'f, A, T: FromUriParam<Query, A> + FromForm<'f>> FromUriParam<Query, A> for Lenient<T>

type Target = <T as FromUriParam<Query, A>>::Target

The resulting type of this conversion.

fn from_uri_param(param: A) -> Self::Target

Converts a value of type T into a value of type Self::Target. The resulting value of type Self::Target will be rendered into a URI using its UriDisplay implementation.

impl<T: Hash> Hash for Lenient<T>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: Ord> Ord for Lenient<T>

fn cmp(&self, other: &Lenient<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T: PartialEq> PartialEq for Lenient<T>

fn eq(&self, other: &Lenient<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: PartialOrd> PartialOrd for Lenient<T>

fn partial_cmp(&self, other: &Lenient<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: Eq> Eq for Lenient<T>

impl<T> StructuralPartialEq for Lenient<T>