Struct value_bag::ValueBag

pub struct ValueBag<'v> { /* fields omitted */ }

A dynamic structured value.

Capturing values

There are a few ways to capture a value:

• Using the ValueBag::capture_* methods.
• Using the standard From trait.
• Using the Fill API.

Using the ValueBag::capture_* methods

ValueBag offers a few constructor methods that capture values of different kinds. These methods require a T: 'static to support downcasting.

use value_bag::ValueBag;

let value = ValueBag::capture_debug(&42i32);

assert_eq!(Some(42), value.to_i32());

Using the standard From trait

Standard types that implement ToValue also implement From.

use value_bag::ValueBag;

let value = ValueBag::from(42i32);

assert_eq!(Some(42), value.to_i32());

use value_bag::ValueBag;

let value = ValueBag::from_debug(&42i32);

assert_eq!(None, value.to_i32());

Using the Fill API

The Fill trait is a way to bridge APIs that may not be directly compatible with other constructor methods.

use value_bag::{ValueBag, Error, fill::{Slot, Fill}};

struct FillSigned;

impl Fill for FillSigned {
    fn fill(&self, slot: &mut Slot) -> Result<(), Error> {
        slot.fill_any(42i32)
    }
}

let value = ValueBag::from_fill(&FillSigned);

assert_eq!(Some(42), value.to_i32());

use value_bag::{ValueBag, Error, fill::{Slot, Fill}};

struct FillDebug;

impl Fill for FillDebug {
    fn fill(&self, slot: &mut Slot) -> Result<(), Error> {
        slot.fill_debug(&42i32 as &dyn Debug)
    }
}

let value = ValueBag::from_fill(&FillDebug);

assert_eq!(None, value.to_i32());

Inspecting values

Once you have a ValueBag there are also a few ways to inspect it:

• Using the Debug, Display, Serialize, and Stream trait implementations.
• Using the ValueBag::to_* methods.
• Using the ValueBag::downcast_ref method.

Implementations

impl<'v> ValueBag<'v>

pub fn from_fill<T>(value: &'v T) -> Self where
    T: Fill, 

Get a value from a fillable slot.

impl<'v> ValueBag<'v>

pub fn to_str(&self) -> Option<Cow<'_, str>>

Try get a str from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones. If the serialization implementation produces a short lived string it will be allocated.

impl<'v> ValueBag<'v>

pub fn to_usize(&self) -> Option<usize>

Try get a usize from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_u8(&self) -> Option<u8>

Try get a u8 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_u16(&self) -> Option<u16>

Try get a u16 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_u32(&self) -> Option<u32>

Try get a u32 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_u64(&self) -> Option<u64>

Try get a u64 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_isize(&self) -> Option<isize>

Try get a isize from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_i8(&self) -> Option<i8>

Try get a i8 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_i16(&self) -> Option<i16>

Try get a i16 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_i32(&self) -> Option<i32>

Try get a i32 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_i64(&self) -> Option<i64>

Try get a i64 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_f32(&self) -> Option<f32>

Try get a f32 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_f64(&self) -> Option<f64>

Try get a f64 from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_bool(&self) -> Option<bool>

Try get a bool from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_char(&self) -> Option<char>

Try get a char from this value.

This method is cheap for primitive types, but may call arbitrary serialization implementations for complex ones.

pub fn to_borrowed_str(&self) -> Option<&str>

Try get a str from this value.

This method is cheap for primitive types. It won't allocate an owned String if the value is a complex type.

pub fn is<T: 'static>(&self) -> bool

Check whether this value can be downcast to T.

pub fn downcast_ref<T: 'static>(&self) -> Option<&T>

Try downcast this value to T.

impl<'v> ValueBag<'v>

pub fn capture_debug<T>(value: &'v T) -> Self where
    T: Debug + 'static, 

Get a value from a debuggable type.

This method will attempt to capture the given value as a well-known primitive before resorting to using its Debug implementation.

pub fn capture_display<T>(value: &'v T) -> Self where
    T: Display + 'static, 

Get a value from a displayable type.

This method will attempt to capture the given value as a well-known primitive before resorting to using its Display implementation.

pub fn from_debug<T>(value: &'v T) -> Self where
    T: Debug, 

Get a value from a debuggable type without capturing support.

pub fn from_display<T>(value: &'v T) -> Self where
    T: Display, 

Get a value from a displayable type without capturing support.

pub fn from_dyn_debug(value: &'v dyn Debug) -> Self

Get a value from a debuggable type without capturing support.

pub fn from_dyn_display(value: &'v dyn Display) -> Self

Get a value from a displayable type without capturing support.

impl<'v> ValueBag<'v>

pub fn capture_serde1<T>(value: &'v T) -> Self where
    T: Serialize + 'static, 

Get a value from a structured type.

This method will attempt to capture the given value as a well-known primitive before resorting to using its Value implementation.

pub fn from_serde1<T>(value: &'v T) -> Self where
    T: Serialize, 

Get a value from a structured type without capturing support.

impl<'v> ValueBag<'v>

pub fn capture_sval1<T>(value: &'v T) -> Self where
    T: Value + 'static, 

Get a value from a structured type.

This method will attempt to capture the given value as a well-known primitive before resorting to using its Value implementation.

pub fn from_sval1<T>(value: &'v T) -> Self where
    T: Value, 

Get a value from a structured type without capturing support.

pub fn from_dyn_sval1(value: &'v dyn Value) -> Self

Get a value from an erased structured type.

Trait Implementations

impl<'v> Clone for ValueBag<'v>

fn clone(&self) -> ValueBag<'v>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'v> Debug for ValueBag<'v>

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

Formats the value using the given formatter.

impl<'v> Display for ValueBag<'v>

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

Formats the value using the given formatter.

impl<'v> From<&'v str> for ValueBag<'v>

fn from(value: &'v str) -> Self

Performs the conversion.

impl<'v> From<()> for ValueBag<'v>

fn from(value: ()) -> Self

Performs the conversion.

impl<'v> From<bool> for ValueBag<'v>

fn from(value: bool) -> Self

Performs the conversion.

impl<'v> From<char> for ValueBag<'v>

fn from(value: char) -> Self

Performs the conversion.

impl<'v> From<f32> for ValueBag<'v>

fn from(value: f32) -> Self

Performs the conversion.

impl<'v> From<f64> for ValueBag<'v>

fn from(value: f64) -> Self

Performs the conversion.

impl<'v> From<i16> for ValueBag<'v>

fn from(value: i16) -> Self

Performs the conversion.

impl<'v> From<i32> for ValueBag<'v>

fn from(value: i32) -> Self

Performs the conversion.

impl<'v> From<i64> for ValueBag<'v>

fn from(value: i64) -> Self

Performs the conversion.

impl<'v> From<i8> for ValueBag<'v>

fn from(value: i8) -> Self

Performs the conversion.

impl<'v> From<isize> for ValueBag<'v>

fn from(value: isize) -> Self

Performs the conversion.

impl<'v> From<u16> for ValueBag<'v>

fn from(value: u16) -> Self

Performs the conversion.

impl<'v> From<u32> for ValueBag<'v>

fn from(value: u32) -> Self

Performs the conversion.

impl<'v> From<u64> for ValueBag<'v>

fn from(value: u64) -> Self

Performs the conversion.

impl<'v> From<u8> for ValueBag<'v>

fn from(value: u8) -> Self

Performs the conversion.

impl<'v> From<usize> for ValueBag<'v>

fn from(value: usize) -> Self

Performs the conversion.

impl<'v> Serialize for ValueBag<'v>

fn serialize<S>(&self, s: S) -> Result<S::Ok, S::Error> where
    S: Serializer, 

Serialize this value into the given Serde serializer.

impl<'v> Value for ValueBag<'v>

fn stream(&self, s: &mut Stream<'_>) -> Result

Stream this value.