Trait FieldValue 

pub trait FieldValue: Sized + 'static {
    // Required method
    fn from_field_text(text: &str) -> Result<Self, FieldValueError>;
}

A field’s value converted from its submitted text, the conversion trait for scalar fields.

String, the integer types, f32, f64, and bool implement it, as does an enumeration with #[derive(FieldValue)]. Implement it for a type of your own to accept that type as a field, with the text converted by your code: a failure is an invalid_type violation, like any other.

The text is valid UTF-8, whatever character set the part declared, since text in another character set is refused before it is converted.

use base_web_content::{FieldValue, FieldValueError};

/// A colour written as `#rrggbb`.
struct Colour(u32);

impl FieldValue for Colour {
    fn from_field_text(text: &str) -> Result<Self, FieldValueError> {
        let digits = text.strip_prefix('#').filter(|digits| digits.len() == 6 && digits.bytes().all(|byte| byte.is_ascii_hexdigit()));
        let digits = digits.ok_or(FieldValueError)?;
        u32::from_str_radix(digits, 16).map(Colour).map_err(|_| FieldValueError)
    }
}

assert_eq!(Colour::from_field_text("#ff8000").map(|colour| colour.0), Ok(0xff8000));
assert!(Colour::from_field_text("orange").is_err());

Required Methods

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

The value the text spells.

Errors

FieldValueError when the text does not spell a value of this type.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl FieldValue for String

Any text, unchanged.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for bool

Exactly true or false.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for f32

A finite decimal number with an optional sign, fraction, and exponent. Whitespace, _ separators, hexadecimal, and NaN or infinity in any spelling, including a number too large for the type, are refused.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for f64

A finite decimal number with an optional sign, fraction, and exponent. Whitespace, _ separators, hexadecimal, and NaN or infinity in any spelling, including a number too large for the type, are refused.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for i8

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for i16

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for i32

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for i64

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for i128

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for isize

An optional + or - followed by one or more ASCII decimal digits, within the type’s range.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for u8

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for u16

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for u32

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for u64

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for u128

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

impl FieldValue for usize

An optional + or - followed by one or more ASCII decimal digits, within the type’s range, so -0 is zero.

fn from_field_text(text: &str) -> Result<Self, FieldValueError>

Implementors