Deferred props

Inertia's deferred props feature allows you to defer the loading of certain page data until after the initial page render. This can be useful for improving the perceived performance of your app by allowing the initial page render to happen as quickly as possible.

Server side

To defer a prop, you can use the defer method when returning your response. This method receives a callback that returns the prop data. The callback will be executed in a separate request after the initial page render.

class UsersController < ApplicationController
  def index
    render inertia: 'Users/Index', props: {
      users: -> { User.all },
      roles: -> { Role.all },
      permissions: InertiaRails.defer { Permission.all },

      # Also works with a lambda:
      # permissions: InertiaRails.defer(-> { Permission.all }),

      # Also works with a simple value,
      # but this way the prop is always evaluated,
      # even if not included:
      # permissions: InertiaRails.defer(Permission.all),
    }
  end
end

Grouping requests

By default, all deferred props get fetched in one request after the initial page is rendered, but you can choose to fetch data in parallel by grouping props together.

class UsersController < ApplicationController
  def index
    render inertia: 'Users/Index', props: {
      users: -> { User.all },
      roles: -> { Role.all },
      permissions: InertiaRails.defer { Permission.all },
      # using block:
      teams: InertiaRails.defer(group: 'attributes') { Team.all },
      # using lambda:
      projects: InertiaRails.defer(-> { Project.all }, group: 'attributes'),
      tasks: InertiaRails.defer(-> { Task.all }, group: 'attributes'),
    }
  end
end

In the example above, the teams, projects, and tasks props will be fetched in one request, while the permissions prop will be fetched in a separate request in parallel. Group names are arbitrary strings and can be anything you choose.

Client side

On the client side, Inertia provides the Deferred component to help you manage deferred props. This component will automatically wait for the specified deferred props to be available before rendering its children.

<script setup>
import { Deferred } from '@inertiajs/vue3'
</script>

<template>
  <Deferred data="permissions">
    <template #fallback>
      <div>Loading...</div>
    </template>
    <div v-for="permission in permissions">
      <!-- ... -->
    </div>
  </Deferred>
</template>

If you need to wait for multiple deferred props to become available, you can specify an array to the data prop.

<script setup>
import { Deferred } from '@inertiajs/vue3'
</script>

<template>
  <Deferred :data="['teams', 'users']">
    <template #fallback>
      <div>Loading...</div>
    </template>
    <!-- Props are now loaded -->
  </Deferred>
</template>