50 lines
1.3 KiB
Plaintext
50 lines
1.3 KiB
Plaintext
:title
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ONCE
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:sig
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ONCE(Request& context)
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:see
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>1_COMPONENT
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>1_INIT
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>1_RENDER
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>1_WS
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>3_C++ Preprocessor
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>unit_call
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:content
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Defines a request-local one-time hook for the current `.uce` unit.
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When a request first enters a given file through `RENDER(Request& context)`, `COMPONENT(Request& context)`, or any `COMPONENT:NAME(Request& context)` handler, the runtime checks whether that unit exposes `ONCE(Request& context)`. If it does, the hook runs before the selected render or component handler.
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`ONCE()` is tracked per request and per resolved unit file, so repeated component calls to the same file inside one request do not rerun it.
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## Typical Uses
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- prepare request-local derived state on `context.call`
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- load request-scoped config or data needed by multiple named component handlers
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- normalize shared props before the unit's first render/component call
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## Example
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```cpp
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ONCE(Request& context)
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{
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context.call["card_defaults"]["tone"] = "info";
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}
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COMPONENT(Request& context)
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{
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<>
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<div class="card card-<?= context.call["card_defaults"]["tone"] ?>">
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<?: component(":BODY", context.props, context) ?>
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</div>
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</>
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}
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```
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## Related Concepts
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- PHP: per-request bootstrap work before a template or partial first runs
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- JavaScript / Node.js: request-scoped lazy initialization before a route or component render
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