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
ToValuetrait. - Using the standard
Fromtrait.
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
sourceimpl<'v> Value<'v>
impl<'v> Value<'v>
sourcepub fn from_any<T>(value: &'v T) -> Self where
T: ToValue,
pub fn from_any<T>(value: &'v T) -> Self where
T: ToValue,
Get a value from a type implementing ToValue.
sourcepub fn capture_debug<T>(value: &'v T) -> Self where
T: Debug + 'static,
pub fn capture_debug<T>(value: &'v T) -> Self where
T: Debug + 'static,
Get a value from a type implementing std::fmt::Debug.
sourcepub fn capture_display<T>(value: &'v T) -> Self where
T: Display + 'static,
pub fn capture_display<T>(value: &'v T) -> Self where
T: Display + 'static,
Get a value from a type implementing std::fmt::Display.
sourcepub fn from_debug<T>(value: &'v T) -> Self where
T: Debug,
pub fn from_debug<T>(value: &'v T) -> Self where
T: Debug,
Get a value from a type implementing std::fmt::Debug.
sourcepub fn from_display<T>(value: &'v T) -> Self where
T: Display,
pub fn from_display<T>(value: &'v T) -> Self where
T: Display,
Get a value from a type implementing std::fmt::Display.
sourcepub fn from_dyn_debug(value: &'v dyn Debug) -> Self
pub fn from_dyn_debug(value: &'v dyn Debug) -> Self
Get a value from a dynamic std::fmt::Debug.
sourcepub fn from_dyn_display(value: &'v dyn Display) -> Self
pub fn from_dyn_display(value: &'v dyn Display) -> Self
Get a value from a dynamic std::fmt::Display.
sourcepub fn downcast_ref<T: 'static>(&self) -> Option<&T>
pub fn downcast_ref<T: 'static>(&self) -> Option<&T>
Try downcast this value to T.
sourceimpl<'v> Value<'v>
impl<'v> Value<'v>
sourcepub fn to_borrowed_str(&self) -> Option<&str>
pub fn to_borrowed_str(&self) -> Option<&str>
Try convert this value into a borrowed string.
Trait Implementations
Auto Trait Implementations
impl<'v> !RefUnwindSafe for Value<'v>
impl<'v> !Send for Value<'v>
impl<'v> !Sync for Value<'v>
impl<'v> Unpin for Value<'v>
impl<'v> !UnwindSafe for Value<'v>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcepub fn borrow_mut(&mut self) -> &mut T
pub fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more