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Nanaloveyuki
74 lines
2.2 KiB
Markdown
74 lines
2.2 KiB
Markdown
---
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name: record-formatter
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group: api
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category: helper
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update-time: 20260613
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description: Public formatter function type used to render records into strings.
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key-word:
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- formatter
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- record
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- text
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- public
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---
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## Record-formatter
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`RecordFormatter` is the public function type used for rendering a `Record` into a `String`. It is the shared shape behind helpers such as `format_text(...)`, custom formatter closures, and sinks that accept formatter functions.
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### Interface
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```moonbit
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pub type RecordFormatter = @utils.RecordFormatter
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```
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#### output
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- `RecordFormatter` - A function type equivalent to `(Record) -> String`.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- This is a type alias, not a new runtime wrapper.
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- Any function matching `(Record) -> String` can be used wherever a `RecordFormatter` is expected.
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- Formatter values are used by `formatted_console_sink(...)`, `formatted_callback_sink(...)`, and text-formatting helpers.
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- The alias exists to make rendering-oriented APIs clearer and easier to read in public signatures.
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### How to Use
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Here are some specific examples provided.
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#### When Need A Custom Formatting Function
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When a sink should render records with custom output rules:
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```moonbit
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let formatter : RecordFormatter = fn(rec) { rec.level.label() + ": " + rec.message }
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let sink = formatted_console_sink(formatter)
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```
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In this example, the alias makes the custom renderer shape explicit.
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#### When Pass A Formatter Through Higher-level APIs
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When application code should accept any formatter function:
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```moonbit
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fn make_sink(formatter : RecordFormatter) -> FormattedConsoleSink {
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formatted_console_sink(formatter)
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}
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```
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In this example, the alias communicates that the parameter is a record-to-string renderer.
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### Error Case
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e.g.:
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- A formatter that omits important fields or level information can make output harder to interpret.
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- A formatter that performs heavy work on every record can add noticeable runtime cost.
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### Notes
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1. Use the alias when function signatures should communicate rendering intent clearly.
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2. `text_formatter(...)` plus `format_text(...)` is usually the better default for configurable human-readable output.
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