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BitLogger/docs/api/record-copy.md
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2026-06-13 21:10:58 +08:00

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---
name: record-copy
group: api
category: record
update-time: 20260613
description: Return a shallow copy of a record without changing any of its fields.
key-word:
- record
- copy
- helper
- public
---
## Record-copy
Return a copy of a `Record` with the same field values. This helper is useful when code wants an explicit independent record value before passing it to sinks, patches, or other downstream steps.
### Interface
```moonbit
pub fn Record::copy(self : Record) -> Record {}
```
#### input
- `self : Record` - Base record that should be copied.
#### output
- `Record` - New record value containing the same `level`, `message`, `timestamp_ms`, `target`, and `fields`.
### Explanation
Detailed rules explaining key parameters and behaviors
- This helper returns a new `Record` value instead of reusing the original one directly.
- `level`, `message`, `timestamp_ms`, `target`, and `fields` are preserved unchanged.
- It is the narrowest explicit duplication helper for a record value.
- This is useful when a downstream path should receive its own record value even though the event data does not change.
### How to Use
Here are some specific examples provided.
#### When Need An Explicit Duplicate For Fanout-style Handling
When one path should keep the current record value while another path continues independently:
```moonbit
let rec = Record::new(Level::Info, "started", target="svc")
let duplicate = rec.copy()
```
In this example, the caller gets a second `Record` value with the same event data.
#### When Need A Stable Baseline Before Later Transformations
When one value should be copied before applying further replacement helpers:
```moonbit
let base = Record::new(Level::Warn, "retry")
let patched = base.copy().with_target("jobs.retry")
```
In this example, the copy step makes the later transformation intent explicit.
### Error Case
e.g.:
- `Record::copy()` itself does not have a runtime failure mode.
- If the code does not actually need a second record value, copying adds no new information and may be unnecessary.
### Notes
1. Use this helper when explicit value duplication improves clarity.
2. It pairs naturally with later `Record` transformation helpers when one path should preserve a baseline value first.