Struct log::kv::Value

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

A value in a structured key-value pair.

Capturing values

There are a few ways to capture a value:

• Using the Value::capture_* methods.
• Using the Value::from_* methods.
• Using the ToValue trait.
• Using the standard From trait.

Using the Value::capture_* methods

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

use log::kv::Value;

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

assert_eq!(Some(42), value.to_i64());

Using the Value::from_* methods

Value offers a few constructor methods that capture values of different kinds. These methods don’t require T: 'static, but can’t support downcasting.

use log::kv::Value;

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

assert_eq!(None, value.to_i64());

Using the ToValue trait

The ToValue trait can be used to capture values generically. It’s the bound used by Source.

let value = 42i32.to_value();

assert_eq!(Some(42), value.to_i64());

use log::kv::ToValue;

let value = (&42i32 as &dyn Debug).to_value();

assert_eq!(None, value.to_i64());

Using the standard From trait

Standard types that implement ToValue also implement From.

use log::kv::Value;

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

assert_eq!(Some(42), value.to_i64());

Implementations

impl<'v> Value<'v>

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

Get a value from a type implementing ToValue.

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

Get a value from a type implementing std::fmt::Debug.

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

Get a value from a type implementing std::fmt::Display.

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

Get a value from a type implementing std::fmt::Debug.

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

Get a value from a type implementing std::fmt::Display.

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

Get a value from a dynamic std::fmt::Debug.

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

Get a value from a dynamic std::fmt::Display.

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> Value<'v>

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

Try convert this value into a u64.

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

Try convert this value into a i64.

pub fn to_u128(&self) -> Option<u128>

Try convert this value into a u128.

pub fn to_i128(&self) -> Option<i128>

Try convert this value into a i128.

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

Try convert this value into a f64.

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

Try convert this value into a char.

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

Try convert this value into a bool.

impl<'v> Value<'v>

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

Try convert this value into a borrowed string.

Trait Implementations

impl<'v> Debug for Value<'v>

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

Formats the value using the given formatter.

impl<'v> Display for Value<'v>

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

Formats the value using the given formatter.

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

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

Performs the conversion.

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

fn from(value: bool) -> Self

Performs the conversion.

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

fn from(value: char) -> Self

Performs the conversion.

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

fn from(value: f32) -> Self

Performs the conversion.

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

fn from(value: f64) -> Self

Performs the conversion.

impl<'v> From<i128> for Value<'v>

fn from(value: i128) -> Self

Performs the conversion.

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

fn from(value: i16) -> Self

Performs the conversion.

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

fn from(value: i32) -> Self

Performs the conversion.

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

fn from(value: i64) -> Self

Performs the conversion.

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

fn from(value: i8) -> Self

Performs the conversion.

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

fn from(value: isize) -> Self

Performs the conversion.

impl<'v> From<u128> for Value<'v>

fn from(value: u128) -> Self

Performs the conversion.

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

fn from(value: u16) -> Self

Performs the conversion.

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

fn from(value: u32) -> Self

Performs the conversion.

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

fn from(value: u64) -> Self

Performs the conversion.

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

fn from(value: u8) -> Self

Performs the conversion.

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

fn from(value: usize) -> Self

Performs the conversion.

impl<'v> ToValue for Value<'v>

fn to_value(&self) -> Value<'_>

Perform the conversion.