React Example: Optimistic Updates Ui

Github StackBlitz CodeSandbox

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 ( <div> <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> <br /> {todoQuery.isSuccess && ( <> <div> {/* The type of queryInfo.data will be narrowed because we check for isSuccess first */} Updated At: {new Date(todoQuery.data.ts).toLocaleTimeString()} </div> <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} </div> ) } export default function App() { return ( <QueryClientProvider client={client}> <Example /> <ReactQueryDevtools initialIsOpen /> </QueryClientProvider> ) } 

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 ( <div> <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> <br /> {todoQuery.isSuccess && ( <> <div> {/* The type of queryInfo.data will be narrowed because we check for isSuccess first */} Updated At: {new Date(todoQuery.data.ts).toLocaleTimeString()} </div> <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} </div> ) } export default function App() { return ( <QueryClientProvider client={client}> <Example /> <ReactQueryDevtools initialIsOpen /> </QueryClientProvider> ) }