BitLogger/docs/api/logger-child.md

name, group, category, update-time, description, key-word

name	group	category	update-time	description	key-word
logger-child	api	logging	20260512	Derive a child logger by composing the current target with a child target segment.	logger target child public

Logger-child

Create a child logger by composing the current target with another target segment. This is the standard API for hierarchical target naming such as app.worker or service.http.client.

Interface

pub fn[S] Logger::child(self : Logger[S], target : String) -> Logger[S] {}

input

• self : Logger[S] - Parent logger whose target should be extended.
• target : String - Child target segment or suffix.

output

• Logger[S] - A new logger whose default target is the composed child path.

Explanation

Detailed rules explaining key parameters and behaviors

• If the parent target is empty, the child target becomes the full target.
• If the child target is empty, the parent target is preserved.
• If both are non-empty, they are joined with ..
• Sink, min level, and timestamp settings are preserved in the returned logger.

How to Use

Here are some specific examples provided.

When Need Hierarchical Target Naming

When subsystem logs should stay grouped under a shared namespace:

let logger = Logger::new(console_sink(), target="service")
let worker = logger.child("worker")

In this example, worker emits records under service.worker.

When Build Deeply Scoped Loggers Step By Step

When deeper target composition should remain readable:

let http = Logger::new(console_sink(), target="app")
  .child("http")
  .child("client")

In this example, the final logger target becomes app.http.client.

Error Case

e.g.:

• If target is empty, the returned logger keeps the original parent target.

• If callers need complete replacement rather than composition, with_target(...) should be used instead.

Notes

Notes are here.

1. This is the preferred API for hierarchical logger naming.

2. Composition uses . as the separator between parent and child segments.

3. The original logger is not mutated.

4. This API works well with with_context_fields(...) to align target and metadata scopes.