useDLE() - [D]ata [L]oading [E]rror

High performance async data rendering without overfetching. With fetch meta data.

In case you cannot use suspense, useDLE() is just like useSuspense() but returns [D]ata [L]oading [E]rror values.

useDLE() is reactive to data mutations; rerendering only when necessary.

Usage

ProfileResource

ProfileList.vue

<script setup lang="ts">
  import { useDLE } from '@data-client/vue';
  import { ProfileResource } from './ProfileResource';

  const { data, loading, error } = useDLE(ProfileResource.getList);
</script>

<template>
  <div v-if="error">Error {{ error.status }}</div>
  <Loading v-else-if="loading || !data" />
  <div v-else>
    <div class="listItem" v-for="profile in data" :key="profile.pk()">
      <Avatar :src="profile.avatar" />
      <div>
        <h4>{{ profile.fullName }}</h4>
        <p>{{ profile.bio }}</p>
      </div>
    </div>
  </div>
</template>

Behavior

data, loading and error are each a ComputedRef. Destructure them at the top level of <script setup> so they are unwrapped in the template. The table below describes their .value.

Expiry Status	Fetch	Data	Loading	Error	Conditions
Invalid	yes1	undefined	true	false	not in store, deletion, invalidation, invalidIfStale
Stale	yes1	denormalized	false	false	(first-render, arg change) & expiry < now
Valid	no	denormalized	false	maybe2	fetch completion
	no	undefined	false	false	null used as second argument

note

1. Identical fetches are automatically deduplicated
2. Hard errors to be caught by onErrorCaptured()

:::

Conditional Dependencies

Use null as the second argument to any Data Client hook means "do nothing."

// todo could be undefined if id is undefined
const todo = useDLE(
  TodoResource.get,
  computed(() => (id.value ? { id: id.value } : null)),
);

Types

function useDLE(
  endpoint: ReadEndpoint,
  ...args: MaybeRefsOrGetters<Parameters<typeof endpoint>> | [null]
): {
  data: ComputedRef<DenormalizeNullable<typeof endpoint.schema>>;
  loading: ComputedRef<boolean>;
  error: ComputedRef<ErrorTypes | undefined>;
};

Arguments can be plain values or refs (including computed); the results update when they change.

Examples

Detail

ProfileResource

ProfileDetail.vue

<script setup lang="ts">
  import { useDLE } from '@data-client/vue';
  import { ProfileResource } from './ProfileResource';

  const {
    data: profile,
    loading,
    error,
  } = useDLE(ProfileResource.get, { id: 1 });
</script>

<template>
  <div v-if="error">Error {{ error.status }}</div>
  <Loading v-else-if="loading || !profile" />
  <div v-else class="listItem">
    <Avatar :src="profile.avatar" />
    <div>
      <h4>{{ profile.fullName }}</h4>
      <p>{{ profile.bio }}</p>
    </div>
  </div>
</template>

Conditional

null will avoid binding and fetching data

▶Resources

▶PostWithAuthor.vue

<script setup lang="ts">
  import { computed } from 'vue';
  import { useDLE } from '@data-client/vue';
  import { PostResource, UserResource } from './Resources';

  const props = defineProps<{ id: string }>();
  const {
    data: post,
    loading: postLoading,
    error: postError,
  } = useDLE(PostResource.get, { id: props.id });
  const {
    data: author,
    loading: authorLoading,
    error: authorError,
  } = useDLE(
    UserResource.get,
    computed(() =>
      post.value?.userId
        ? {
            id: post.value.userId,
          }
        : null,
    ),
  );
</script>

<template>
  <div v-if="postError">Error {{ postError.status }}</div>
  <Loading v-else-if="postLoading || !post" />
  <div v-else-if="authorError">Error {{ authorError.status }}</div>
  <Loading v-else-if="authorLoading || !author" />
  <div v-else>{{ author.username }}</div>
</template>

Embedded data

When entities are stored in nested structures, that structure will remain.

▶api/Post

export class PaginatedPost extends Entity {
  id = '';
  title = '';
  content = '';

  static key = 'PaginatedPost';
}

export const getPosts = new RestEndpoint({
  path: '/post',
  searchParams: { page: '' },
  schema: {
    results: new Collection([PaginatedPost]),
    nextPage: '',
    lastPage: '',
  },
});

▶ArticleList.vue

<script setup lang="ts">
  import { useDLE } from '@data-client/vue';
  import { getPosts } from './api/Post';

  const props = defineProps<{ page: string }>();
  const { data, loading, error } = useDLE(getPosts, { page: props.page });
</script>

<template>
  <div v-if="error">Error {{ error.status }}</div>
  <Loading v-else-if="loading || !data" />
  <div v-else>
    <div v-for="post in data.results" :key="post.pk()">
      {{ post.title }}
    </div>
  </div>
</template>