# tracing_core::Event - Rust
API documentation for the Rust `Event` struct in crate `tracing_core`.
Keywords: rust, rustlang, rust-lang, Event

# Struct tracing_core::Event [−] [src]

    pub struct Event<'a> { /* fields omitted */ }

`Event`s represent single points in time where something occurred during the execution of a program.

An `Event` can be compared to a log record in unstructured logging, but with two key differences:

- `Event`s exist within the context of a span. Unlike log lines, they may be located within the trace tree, allowing visibility into the temporal context in which the event occurred, as well as the source code location.
- Like spans, `Event`s have structured key-value data known as fields, which may include textual message. In general, a majority of the data associated with an event should be in the event's fields rather than in the textual message, as the fields are more structured.

## Implementations

### `impl<'a> Event<'a>` [src]

#### `pub fn dispatch(metadata: &'static Metadata<'static>, fields: &'a ValueSet<'_>)` [src]

Constructs a new `Event` with the specified metadata and set of values, and observes it with the current subscriber.

#### `pub fn new(
metadata: &'static Metadata<'static>,
fields: &'a ValueSet<'a>
) -> Self` [src]

Returns a new `Event` in the current span, with the specified metadata and set of values.

#### `pub fn new_child_of(
parent: impl Into<Option<Id>>,
metadata: &'static Metadata<'static>,
fields: &'a ValueSet<'a>
) -> Self` [src]

Returns a new `Event` as a child of the specified span, with the provided metadata and set of values.

#### `pub fn child_of(
parent: impl Into<Option<Id>>,
metadata: &'static Metadata<'static>,
fields: &'a ValueSet<'_>
)` [src]

Constructs a new `Event` with the specified metadata and set of values, and observes it with the current subscriber and an explicit parent.

#### `pub fn record(&self, visitor: &mut dyn Visit)` [src]

Visits all the fields on this `Event` with the specified visitor.

#### `pub fn fields(&self) -> Iterⓘ

### Notable traits for Iter

`impl Iterator for Iter type Item = Field;`
` [src]

Returns an iterator over the set of values on this `Event`.

#### `pub fn metadata(&self) -> &'static Metadata<'static>` [src]

Returns metadata describing this `Event`.

#### `pub fn is_root(&self) -> bool` [src]

Returns true if the new event should be a root.

#### `pub fn is_contextual(&self) -> bool` [src]

Returns true if the new event's parent should be determined based on the current context.

If this is true and the current thread is currently inside a span, then that span should be the new event's parent. Otherwise, if the current thread is not inside a span, then the new event will be the root of its own trace tree.

#### `pub fn parent(&self) -> Option<&Id>` [src]

Returns the new event's explicitly-specified parent, if there is one.

Otherwise (if the new event is a root or is a child of the current span), returns false.

## Trait Implementations

### `impl<'a> Debug for Event<'a>` [src]

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl<'a> !RefUnwindSafe for Event<'a>` [src]

### `impl<'a> !Send for Event<'a>` [src]

### `impl<'a> !Sync for Event<'a>` [src]

### `impl<'a> Unpin for Event<'a>` [src]

### `impl<'a> !UnwindSafe for Event<'a>` [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, U> Into<U> for T where
U: From<T>,` [src]

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

Performs the conversion.

### `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.