Optimistic updates not working?

Does anyone have a working code snippet using the latest create t3?

2 Replies

dan•13mo ago

Include the code here and someone will might be able to see whats wrong. There are examples on the react query docs on setting up optimistic updates, you can do the same with trpc. https://tanstack.com/query/latest/docs/react/guides/optimistic-updates

Optimistic Updates | TanStack Query Docs

When you optimistically update your state before performing a mutation, there is a chance that the mutation will fail. In most of these failure cases, you can just trigger a refetch for your optimistic queries to revert them to their true server state. In some circumstances though, refetching may not work correctly and the mutation error could ...

Zion•13mo ago

const { mutate, isLoading } = api.todo.create.useMutation({
    async onMutate(newTodo) {
      resetField("title");
      // Cancel outgoing fetches (so they don't overwrite our optimistic update)
      await utils.todo.userList.cancel();

      // Get the data from the queryCache
      const prevData = utils.todo.userList.getData();

      const optimisticTodo = {
        title: newTodo.title,
        userId: session.data?.user?.id ?? "",
        createdAt: new Date(),
        done: false,
      } as Todo;

      // Optimistically update the data with our new post
      utils.todo.userList.setData(undefined, (old) => [
        optimisticTodo,
        ...(old ?? []),
      ]); // Use updater function

      // Return the previous data so we can revert if something goes wrong
      return { prevData };
    },
    onError(err, newTodo, ctx) {
      // If the mutation fails, use the context-value from onMutate
      utils.todo.userList.setData(undefined, (old) => ctx?.prevData ?? old);
    },
    onSettled() {
      // Sync with server once mutation has settled
      void utils.todo.userList.invalidate();
    },
  });

const { mutate, isLoading } = api.todo.create.useMutation({
    async onMutate(newTodo) {
      resetField("title");
      // Cancel outgoing fetches (so they don't overwrite our optimistic update)
      await utils.todo.userList.cancel();

      // Get the data from the queryCache
      const prevData = utils.todo.userList.getData();

      const optimisticTodo = {
        title: newTodo.title,
        userId: session.data?.user?.id ?? "",
        createdAt: new Date(),
        done: false,
      } as Todo;

      // Optimistically update the data with our new post
      utils.todo.userList.setData(undefined, (old) => [
        optimisticTodo,
        ...(old ?? []),
      ]); // Use updater function

      // Return the previous data so we can revert if something goes wrong
      return { prevData };
    },
    onError(err, newTodo, ctx) {
      // If the mutation fails, use the context-value from onMutate
      utils.todo.userList.setData(undefined, (old) => ctx?.prevData ?? old);
    },
    onSettled() {
      // Sync with server once mutation has settled
      void utils.todo.userList.invalidate();
    },
  });

exmaple for a todo app

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Optimistic updates not working?