Struct LogFields 

pub struct LogFields(/* private fields */);

A set of key-value fields that can be attached to a logging scope.

LogFields stores structured attributes that extend the key-values source of a log::Record. When a record flows through crate::ContextLogger, these fields are merged into the record’s own log::kv::Source so they appear in the output alongside the user-provided key-values.

Ordering

The order in which fields appear is not guaranteed. Do not rely on any specific ordering of keys.

Implementations

impl LogFields

pub fn new() -> Self

Creates a new, empty set of fields.

pub fn with( self, key: impl Into<Cow<'static, str>>, value: impl Into<LogValue>, ) -> Self

Inserts a key-value pair into this collection, returning the collection for chained calls.

This method takes ownership of self, so it can be used as part of a builder-style chain:

Examples

use context_logger::LogFields;

let fields = LogFields::new()
      .with("user_id", "user-123")
      .with("request_id", 42);

pub fn insert( &mut self, key: impl Into<Cow<'static, str>>, value: impl Into<LogValue>, ) -> &mut Self

Inserts a key-value pair into this collection.

Unlike Self::with, this method borrows self and returns a mutable reference, allowing it to be used when chaining with other methods that require borrowing.

Examples

use context_logger::LogFields;

let mut fields = LogFields::new();
fields
    .insert("user_id", "user-123")
    .insert("request_id", 42);

pub fn merge_with( &mut self, other: impl IntoIterator<Item = (Cow<'static, str>, LogValue)>, ) -> &mut Self

Merges this collection with the fields from another one.

This method borrows self and returns a mutable reference, allowing it to be used when chaining with other methods that require borrowing.

Merging policy

Keys in this collection with duplicate names will be overwritten by keys from the provided collection. The order of keys in the resulting collection is undefined.

Examples

use context_logger::LogFields;

let mut fields = LogFields::new();
fields
    .insert("user_id", "Alice")
    .merge_with(other_fields)
    .insert("request_id", 42);

pub fn iter(&self) -> Iter<'_, Cow<'static, str>, LogValue>

Returns an iterator over the fields in this collection.

pub fn is_empty(&self) -> bool

Returns true if this collection contains no fields.

Trait Implementations

impl Clone for LogFields

fn clone(&self) -> LogFields

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LogFields

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

Formats the value using the given formatter.

impl Default for LogFields

fn default() -> LogFields

Returns the “default value” for a type.

impl Extend<(Cow<'static, str>, LogValue)> for LogFields

fn extend<I: IntoIterator<Item = (Cow<'static, str>, LogValue)>>( &mut self, iter: I, )

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl FromIterator<(Cow<'static, str>, LogValue)> for LogFields

fn from_iter<T: IntoIterator<Item = (Cow<'static, str>, LogValue)>>( iter: T, ) -> Self

Creates a value from an iterator.

impl<'a> IntoIterator for &'a LogFields

type Item = (&'a Cow<'static, str>, &'a LogValue)

The type of the elements being iterated over.

type IntoIter = Iter<'a, Cow<'static, str>, LogValue>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl IntoIterator for LogFields

type Item = (Cow<'static, str>, LogValue)

The type of the elements being iterated over.

type IntoIter = IntoIter<Cow<'static, str>, LogValue>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.