# tracing::field::Field - Rust
API documentation for the Rust `Field` struct in crate `tracing`.
Keywords: rust, rustlang, rust-lang, Field

# Struct tracing::field::Field [−] [src]

    pub struct Field { /* fields omitted */ }

An opaque key allowing O(1) access to a field in a `Span`'s key-value data.

As keys are defined by the metadata of a span, rather than by an individual instance of a span, a key may be used to access the same field across all instances of a given span with the same metadata. Thus, when a subscriber observes a new span, it need only access a field by name once, and use the key for that name for all other accesses.

## Implementations

### `impl Field` [src]

#### `pub fn callsite(&self) -> Identifier` [src]

Returns an `Identifier` that uniquely identifies the `Callsite` which defines this field.

#### `pub fn name(&self) -> &'static str` [src]

Returns a string representing the name of the field.

## Trait Implementations

### `impl AsField for Field` [src]

#### `fn as_field(&self, metadata: &Metadata<'_>) -> Option<Field>` [src]

Attempts to convert `&self` into a `Field` with the specified `metadata`. Read more

### `impl<'a> AsField for &'a Field` [src]

#### `fn as_field(&self, metadata: &Metadata<'_>) -> Option<Field>` [src]

Attempts to convert `&self` into a `Field` with the specified `metadata`. Read more

### `impl AsRef<str> for Field` [src]

#### `pub fn as_ref(&self) -> &str` [src]

Performs the conversion.

### `impl Clone for Field` [src]

#### `pub fn clone(&self) -> Field` [src]

Returns a copy of the value. Read more

#### `pub fn clone_from(&mut self, source: &Self)`1.0.0 [src]

Performs copy-assignment from `source`. Read more

### `impl Debug for Field` [src]

#### `pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>` [src]

Formats the value using the given formatter. Read more

### `impl Display for Field` [src]

#### `pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>` [src]

Formats the value using the given formatter. Read more

### `impl Eq for Field` [src]

### `impl Hash for Field` [src]

#### `pub fn hash<H>(&self, state: &mut H) where
H: Hasher,` [src]

Feeds this value into the given `Hasher`. Read more

#### `pub fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0 [src]

Feeds a slice of this type into the given `Hasher`. Read more

### `impl PartialEq<Field> for Field` [src]

#### `pub fn eq(&self, other: &Field) -> bool` [src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `#[must_use]pub fn ne(&self, other: &Rhs) -> bool` 1.0.0 [src]

This method tests for `!=`.

## Auto Trait Implementations

### `impl !RefUnwindSafe for Field` [src]

### `impl Send for Field` [src]

### `impl Sync for Field` [src]

### `impl Unpin for Field` [src]

### `impl !UnwindSafe for Field` [src]

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T> Instrument for T` [src]

#### `fn instrument(self, span: Span) -> Instrumented<Self>ⓘ

### Notable traits for Instrumented<T>

`impl<T: Future> Future for Instrumented<T> type Output = T::Output;`
` [src]

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more

#### `fn in_current_span(self) -> Instrumented<Self>ⓘ

### Notable traits for Instrumented<T>

`impl<T: Future> Future for Instrumented<T> type Output = T::Output;`
` [src]

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `pub fn to_owned(&self) -> T` [src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `pub fn clone_into(&self, target: &mut T)` [src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `pub default fn to_string(&self) -> String` [src]

Converts the given value to a `String`. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.