Search…

Auto

StartRC

Router

Query

Docs

Partners

React React

Latest

Search…

latest

React React

Latest

React Example: Optimistic Updates Ui

Github StackBlitz CodeSandbox

Code ExplorerCode

Interactive SandboxSandbox

src
- pages
  - api
  - index.tsx
.gitignore
README.md
next.config.js
package.json
tsconfig.json

tsx

    import * as React from 'react'
    import {
      QueryClient,
      QueryClientProvider,
      useMutation,
      useQuery,
      useQueryClient,
    } from '@tanstack/react-query'
    import { ReactQueryDevtools } from '@tanstack/react-query-devtools'

    const client = new QueryClient()

    type Todos = {
      items: ReadonlyArray<{
        id: string
        text: string
      }>
      ts: number
    }

    async function fetchTodos(): Promise<Todos> {
      const response = await fetch('/api/data')
      return await response.json()
    }

    function useTodos() {
      return useQuery({ queryKey: ['todos'], queryFn: fetchTodos })
    }

    function Example() {
      const queryClient = useQueryClient()
      const [text, setText] = React.useState('')
      const todoQuery = useTodos()

      const addTodoMutation = useMutation({
        mutationFn: async (newTodo: string) => {
          const response = await fetch('/api/data', {
            method: 'POST',
            body: JSON.stringify({ text: newTodo }),
            headers: { 'Content-Type': 'application/json' },
          })
          if (!response.ok) {
            throw new Error('Something went wrong.')
          }
          return await response.json()
        },
        onSettled: () => queryClient.invalidateQueries({ queryKey: ['todos'] }),
      })

      return (
          <p>
            In this example, new items can be created using a mutation. The new item
            will be optimistically added to the list in hopes that the server
            accepts the item. If it does, the list is refetched with the true items
            from the list. Every now and then, the mutation may fail though. When
            that happens, the previous list of items is restored and the list is
            again refetched from the server.
          </p>
          <form
            onSubmit={(e) => {
              e.preventDefault()
              setText('')
              addTodoMutation.mutate(text)
            }}
          >
            <input
              type="text"
              onChange={(event) => setText(event.target.value)}
              value={text}
            />
            <button disabled={addTodoMutation.isPending}>Create</button>
          </form>
          {todoQuery.isSuccess && (
            <>
                {/* The type of queryInfo.data will be narrowed because we check for isSuccess first */}
                Updated At: {new Date(todoQuery.data.ts).toLocaleTimeString()}
              <ul>
                {todoQuery.data.items.map((todo) => (
                  <li key={todo.id}>{todo.text}</li>
                ))}
                {addTodoMutation.isPending && (
                  <li style={{ opacity: 0.5 }}>{addTodoMutation.variables}</li>
                )}
                {addTodoMutation.isError && (
                  <li style={{ color: 'red' }}>
                    {addTodoMutation.variables}
                    <button
                      onClick={() =>
                        addTodoMutation.mutate(addTodoMutation.variables)
                      }
                    >
                      Retry
                    </button>
                  </li>
                )}
              </ul>
              {todoQuery.isFetching && <div>Updating in background...</div>}
            </>
          )}
          {todoQuery.isPending && 'Loading'}
          {todoQuery.error instanceof Error && todoQuery.error.message}
      )
    }

    export default function App() {
      return (
      )
    }

[Want to Skip the Docs?

“If you’re serious about really understanding React Query, there’s no better way than with query.gg”—Tanner Linsley

Learn More](https://query.gg?s=tanstack)