> This file extends [common/patterns.md](../common/patterns.md) with Vue specific content.
## Composables
- The composable (`useXxx`) is the reusable-logic unit. In Feature-Sliced Design it lives in the slice `model` segment.
- Accept `MaybeRefOrGetter<T>` inputs and normalize with `toValue`, so callers can pass a ref, a getter, or a raw value.
- Return `toRefs(reactive(...))` so consumers can destructure without losing reactivity.
- A composable that uses lifecycle hooks or `provide` / `inject` must be called inside a component `setup`, not lazily or conditionally.
## Props, Emits, v-model
- Type-based `defineProps<Props>()` and tuple-form `defineEmits<{ change: [id: number] }>()`.
-`defineModel<T>('name', { default })` for two-way binding. It compiles to a prop plus an `update:*` emit.
## Provide / Inject
- Use `provide` / `inject` for tree-scoped data without prop drilling.
- Type-safe collision-free keys: `const key = Symbol() as InjectionKey<T>`.
- The provider owns mutations. Expose a `readonly` ref plus an explicit updater function, never a raw mutable ref.
## Pinia (FSD model segment)
- Prefer setup stores: `ref` is state, `computed` is getters, `function` is actions.
- Setup stores do not get `$reset` for free. Define your own.
- Use `storeToRefs` for state and getters. Destructure actions directly off the store.
- Never persist raw auth tokens to `localStorage`.
## vue-router
- Lazy-load route components with dynamic `import()`.
- A global `beforeEach` auth gate keyed on `meta.requiresAuth`. Guards return `false` (cancel), a route location (redirect), or `undefined` / `true` (continue).
- Watch `() => route.params.id`, not the whole `route` object.
