73 lines
2.0 KiB
Markdown
73 lines
2.0 KiB
Markdown
# ViewData (Website Templates)
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ViewData is the **only** allowed input type for Templates in `apps/website`.
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Authoritative contract: [`WEBSITE_CONTRACT.md`](docs/architecture/website/WEBSITE_CONTRACT.md:1).
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## 1) Definition
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ViewData is a JSON-serializable, template-ready data structure:
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- primitives (strings/numbers/booleans)
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- arrays and plain objects
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- `null` for missing values
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## 2) What ViewData is NOT
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ViewData is not:
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- an API Transport DTO (raw transport)
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- a ViewModel (client-only class)
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- a Display Object instance
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## 3) Construction rules
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ViewData is created by **ViewData Builders**:
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### Server Components (RSC)
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```typescript
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const apiDto = await PageQuery.execute();
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const viewData = ViewDataBuilder.build(apiDto);
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return <Template viewData={viewData} />;
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```
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### Client Components
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```typescript
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'use client';
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const [viewModel, setViewModel] = useState<ViewModel | null>(null);
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useEffect(() => {
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const apiDto = await apiClient.get();
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const vm = ViewModelBuilder.build(apiDto);
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setViewModel(vm);
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}, []);
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// Template receives ViewModel, not ViewData
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return viewModel ? <Template viewModel={viewModel} /> : null;
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```
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Templates MUST NOT compute derived values.
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ViewData Builders MUST NOT call the API.
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## 4) Determinism rules
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Any formatting used to produce ViewData MUST be deterministic.
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Forbidden anywhere in formatting code paths:
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- `Intl.*`
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- `Date.toLocaleString()` / `Date.toLocaleDateString()` / `Date.toLocaleTimeString()`
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Reason: SSR and browser outputs can differ.
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Localization MUST NOT depend on runtime locale APIs.
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If localized strings are required, they MUST be provided as deterministic inputs (for example via API-provided labels or a deterministic code-to-label map) and passed through ViewData Builders into ViewData.
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## 5) Relationship to Display Objects
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Display Objects are used to implement formatting/mapping, but their instances MUST NOT be stored inside ViewData.
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Only primitive outputs produced by Display Objects may appear in ViewData.
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