Implementing Optimistic UI in React: A Practical Guide

Introduction

Optimistic UI is a powerful design pattern that can dramatically enhance the user experience by making your application feel faster and more responsive. In a nutshell, Optimistic UI updates the interface immediately upon a user action, without waiting for a server response. When the server's response eventually arrives, the optimistic update is either confirmed or corrected. This blog post will guide you through implementing Optimistic UI in React, culminating in an overview of how Apollo Cache can further refine this pattern.

The Basics of Optimistic UI

What is Optimistic UI?

Optimistic UI is a UI design pattern where, upon a user-initiated action like adding an item to a list, the application updates the UI as if the action has already been completed successfully. This eliminates the delay associated with waiting for server confirmation, making your application feel snappy and reactive.

Why Use Optimistic UI?

1. Enhanced User Experience: Immediate feedback enhances user engagement and satisfaction.
2. Reduced Perceived Latency: Since the UI updates instantly, the app feels faster, even if the server takes time to respond.
3. Graceful Error Handling: If the server responds with an error, the UI can revert the change, thus maintaining data integrity.

Implementing Optimistic UI in React

Step 1: Identify User Actions

Identify the actions where implementing Optimistic UI will enhance the user experience. These are often CRUD operations (Create, Read, Update, Delete).

Step 2: Implementing State Management

Before updating the server, update the client-side state as if the server call has already succeeded. This is the "Optimistic Update."

const [items, setItems] = useState([]);

function addItemOptimistically(newItem) {
  // Optimistic UI update
  setItems([...items, newItem]);

  // Server call
  api.addItem(newItem).then(
    (response) => {
      // Confirm the optimistic update or correct it
    },
    (error) => {
      // Revert the optimistic update
      setItems(items);
    }
  );
}

Step 3: Handle Server Response

Upon receiving the server response, you have two scenarios:

1. Success: The optimistic update is correct, and no further action is needed.
2. Failure: Revert the optimistic update and possibly show an error message.

Enhancing with Apollo Cache

If you're already using Apollo Client for GraphQL in your React application, Apollo Cache is a convenient and powerful way to implement Optimistic UI.

How Does it Work?

Apollo Client's mutate function allows you to specify an optimisticResponse that simulates the expected result of a mutation. This enables Apollo Cache to update the UI optimistically before the server response is received.

const [addTodo] = useMutation(ADD_TODO, {
  optimisticResponse: {
    __typename: "Mutation",
    addTodo: {
      __typename: "Todo",
      id: Math.random(),
      text: "New Todo",
    },
  },
});

Once the real server response arrives, Apollo Cache automatically updates the UI with the actual data, ensuring consistency and correctness.

Conclusion

Optimistic UI is a compelling design pattern for making your React applications feel faster and more responsive. By understanding and implementing this pattern, you'll be well-equipped to tackle real-world challenges that come with latency and server communication. When paired with sophisticated state management solutions like Apollo Cache, Optimistic UI becomes even more potent, providing an optimal user experience without sacrificing data integrity.