diff --git a/docs/config.json b/docs/config.json index 8d14e3c7da..d079a7b020 100644 --- a/docs/config.json +++ b/docs/config.json @@ -99,6 +99,10 @@ "label": "TypeScript", "to": "framework/vue/typescript" }, + { + "label": "Reactivity", + "to": "framework/vue/reactivity" + }, { "label": "GraphQL", "to": "framework/vue/graphql" diff --git a/docs/framework/vue/reactivity.md b/docs/framework/vue/reactivity.md new file mode 100644 index 0000000000..371b32c52c --- /dev/null +++ b/docs/framework/vue/reactivity.md @@ -0,0 +1,166 @@ +--- +id: reactivity +title: Reactivity +--- + +Vue uses the [the signals paradigm](https://vuejs.org/guide/extras/reactivity-in-depth.html#connection-to-signals) to handle and track reactivity. A key feature of +this system is the reactive system only triggers updates on specifically watched reactive properties. A consequence of this is you also need to ensure that the queries are updated when values they consume are updated. + +# Keeping Queries Reactive + +When creating a composable for a query your first choice may be to write it like so: + +```ts +export function useUserProjects(userId: string) { + return useQuery( + queryKey: ['userProjects', userId], + queryFn: () => api.fetchUserProjects(userId), + ); +} +``` + +We might consume this composable like so: + +```ts +// Reactive user ID ref. +const userId = ref('1') +// Fetches the user 1's projects. +const { data: projects } = useUserProjects(userId.value) + +const onChangeUser = (newUserId: string) => { + // Edits the userId, but the query will not re-fetch. + userId.value = newUserId +} +``` + +This code will not work as intended. This is because we are extracting the value from the userId ref directly. Vue-query is not tracking the `userId` `ref` so it has no way of knowing when the value changes. + +Luckily, the fix for this is trivial. The value must be made trackable in the query key. We can Just accept the `ref` directly in the composable and place it in the query key: + +```ts +export function useUserProjects(userId: Ref) { + return useQuery( + queryKey: ['userProjects', userId], + queryFn: () => api.fetchUserProjects(userId.value), + ); +} +``` + +Now the query will re-fetch when the `userId` changes. + +```ts +const onChangeUser = (newUserId: string) => { + // Query refetches data with new user ID! + userId.value = newUserId +} +``` + +In vue query any reactive properties within a query key are tracked for changes automatically. This allows vue-query to refetch data whenever the +parameters for a given request change. + +## Accounting for Non-Reactive Queries + +While far less likely, sometimes passing non-reactive variables is intentional. For example, some entities only need to be fetched once and don't need tracking or we invalidate a mutation a query options object after a mutation. +If we use our custom composable defined above the usage in this case feels a bit off: + +```ts +const { data: projects } = useUserProjects(ref('1')) +``` + +We have to create an intermediate `ref` just to make the parameter type-compatible. We can do better here. Let's instead update our composable to accept both plain values and reactive values: + +```ts +export function useUserProjects(userId: MaybeRef) { + return useQuery( + queryKey: ['userProjects', userId], + queryFn: () => api.fetchUserProjects(toValue(userId)), + ); +} +``` + +Now we can use the composable with both plain values and refs: + +```ts +// Fetches the user 1's projects, userId is not expected to change. +const { data: projects } = useUserProjects('1') + +// Fetches the user 1's projects, queries will react to changes on userId. +const userId = ref('1') + +// Make some changes to userId... + +// Query re-fetches based on any changes to userId. +const { data: projects } = useUserProjects(userId) +``` + +## Using Derived State inside Queries + +It's quite common to derive some new reactive state from another source of reactive state. Commonly, this problem manifests in situations where you deal with component props. Let's assume our `userId` is a prop passed to a component: + +```vue + +``` + +You may be tempted to use the prop directly in the query like so: + +```ts +// Won't react to changes in props.userId. +const { data: projects } = useUserProjects(props.userId) +``` + +However, similar to the first example, this is not reactive. Property access on `reactive` variables causes reactivity to be lost. We can fix this by making this derived state reactive via a `computed`: + +```ts +const userId = computed(() => props.userId) + +// Reacts to changes in props.userId. +const { data: projects } = useUserProjects(userId) +``` + +This works as expected, however, this solution isn't always the most optimal. Aside from the introduction of an intermediate variable, we also create a memoized value that is somewhat unnecessary. For trivial cases of simple property access `computed` is an optimization with no real benefit. In these cases a more appropriate solution is to use [reactive getters](https://blog.vuejs.org/posts/vue-3-3#better-getter-support-with-toref-and-tovalue). Reactive getters are simply functions that return a value based on some reactive state, similar to how `computed` works. Unlike `computed`, reactive getters do not memoize their values so it makes it a good candidate for simple property access. + +Let's once again refactor our composable, but this time we'll have it accept a `ref`, plain value, or a reactive getter: + +```ts +export function useUserProjects(userId: MaybeRefOrGetter) { + ... +} +``` + +Let's adjust our usage and now use a reactive getter: + +```ts +// Reacts to changes in props.userId. No `computed` needed! +const { data: projects } = useUserProjects(() => props.userId) +``` + +This gives us a terse syntax and the reactivity we need without any unneeded memoization overhead. + +## Other tracked Query Options + +Above, we only touched one query option that tracks reactive dependencies. However, in addition to `queryKey`, `enabled` also allows +the use of reactive values. This comes in handy in situations where you want to control the fetching of a query based on some derived state: + +```ts +export function useUserProjects(userId: MaybeRef) { + return useQuery( + queryKey: ['userProjects', userId], + queryFn: () => api.fetchUserProjects(toValue(userId)), + enabled: () => userId.value === activeUserId.value, + ); +} +``` + +More details on this option can be found on the [useQuery reference](./reference/useQuery.md) page. + +# Key Takeaways + +- `enabled` and `queryKey` are the two query options that can accept reactive values. +- Pass query option that accept all three types of values in Vue: refs, plain values, and reactive getters. +- If you expect a query to react to changes based on the values it consumes, ensure that the values are reactive. (i.e. pass in refs directly to the query, or use reactive getters) +- If you don't need a query to be reactive pass in a plain value. +- For trivial derived state such as property access consider using a reactive getter in place of a `computed`.