Struct log::kv::Value

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

Expand description

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§

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impl<'v> Value<'v>

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

Get a value from a type implementing ToValue.

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

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

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

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

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

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

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

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

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

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

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

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

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pub fn is<T: 'static>(&self) -> bool

Check whether this value can be downcast to T.

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

Try downcast this value to T.

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pub fn visit(&self, visitor: impl Visit<'v>) -> Result<(), Error>

Inspect this value using a simple visitor.

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impl<'v> Value<'v>

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

Try convert this value into a u64.

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

Try convert this value into a i64.

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

Try convert this value into a u128.

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

Try convert this value into a i128.

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

Try convert this value into a f64.

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

Try convert this value into a char.

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

Try convert this value into a bool.

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impl<'v> Value<'v>

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

Try convert this value into a borrowed string.

Trait Implementations§

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

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

Formats the value using the given formatter. Read more

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

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

Formats the value using the given formatter. Read more

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