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BitLogger/docs/api/library-logger-info.md
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2026-06-14 01:18:33 +08:00

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---
name: library-logger-info
group: api
category: facade
update-time: 20260613
description: Emit an info-level record through a LibraryLogger facade by delegating to the wrapped logger's info shortcut.
key-word:
- library
- facade
- info
- public
---
## Library-logger-info
Emit an info-level record through the library-facing sync logger. This is the convenience wrapper for `log(Level::Info, ...)` on `LibraryLogger[S]`.
### Interface
```moonbit
pub fn[S : Sink] LibraryLogger::info(
self : LibraryLogger[S],
message : String,
fields~ : Array[Field] = [],
) -> Unit {
```
#### input
- `self : LibraryLogger[S]` - Library-facing logger that should emit the info record.
- `message : String` - Informational message text.
- `fields : Array[Field]` - Optional structured fields attached to the record.
#### output
- `Unit` - No return value. The record is handled according to the current threshold and wrapped sink pipeline.
### Explanation
Detailed rules explaining key parameters and behaviors
- This helper delegates to `info(...)` on the wrapped logger, which in turn uses `log(Level::Info, ...)`.
- `Info` is the default minimum logger threshold unless changed explicitly.
- Per-call target override is not exposed here; use `log(...)` if needed.
- Any existing sink wrappers inside the logger pipeline still participate normally in the write path.
- The library facade keeps the same write semantics while exposing a smaller public surface.
- Broader composition helpers remain on the underlying `Logger[S]` and require `to_logger()` first.
### How to Use
Here are some specific examples provided.
#### When Emit Normal Library Lifecycle Events
When a package should report standard lifecycle milestones:
```moonbit
logger.info("service started")
```
In this example, the event uses normal informational severity through the narrower facade.
#### When Attach Structured Informational Context
When an info event should include machine-readable metadata:
```moonbit
logger.info("request completed", fields=[field("status", "200")])
```
In this example, the event remains concise while still carrying useful fields.
And any shared context already carried by the facade still participates through the wrapped logger pipeline.
### Error Case
e.g.:
- If the logger minimum level is above `Info`, the call returns without writing a record.
- If the event needs an explicit alternate target, use `log(...)` instead of this shortcut.
- If callers need broader composition helpers after logging, they must unwrap first with `to_logger()`.
### Notes
1. This is the common convenience method for normal library-facing events.
2. Because `Info` is often the default threshold, this helper is a natural baseline for facade examples.
3. Use `log(...)` instead when the call site needs a per-call target override or a dynamic level.