React UI Patterns

When to Use

Use this skill when you need modern React UI patterns for loading states, error handling, and data fetching. Use when building UI components, handling async data, or managing UI states.

Core Principles

1. Never show stale UI - Loading spinners only when actually loading
2. Always surface errors - Users must know when something fails
3. Optimistic updates - Make the UI feel instant
4. Progressive disclosure - Show content as it becomes available
5. Graceful degradation - Partial data is better than no data

Loading State Patterns

The Golden Rule

Show loading indicator ONLY when there's no data to display.

// CORRECT - Only show loading when no data exists
const { data, loading, error } = useGetItemsQuery();

if (error) return <ErrorState error={error} onRetry={refetch} />;
if (loading && !data) return <LoadingState />;
if (!data?.items.length) return <EmptyState />;

return <ItemList items={data.items} />;

// WRONG - Shows spinner even when we have cached data
if (loading) return <LoadingState />; // Flashes on refetch!

Loading State Decision Tree

Is there an error?
  → Yes: Show error state with retry option
  → No: Continue

Is it loading AND we have no data?
  → Yes: Show loading indicator (spinner/skeleton)
  → No: Continue

Do we have data?
  → Yes, with items: Show the data
  → Yes, but empty: Show empty state
  → No: Show loading (fallback)

Skeleton vs Spinner

Error Handling Patterns

The Error Handling Hierarchy

1. Inline error (field-level) → Form validation errors
2. Toast notification → Recoverable errors, user can retry
3. Error banner → Page-level errors, data still partially usable
4. Full error screen → Unrecoverable, needs user action

Always Show Errors

CRITICAL: Never swallow errors silently.

// CORRECT - Error always surfaced to user
const [createItem, { loading }] = useCreateItemMutation({
  onCompleted: () => {
    toast.success({ title: 'Item created' });
  },
  onError: (error) => {
    console.error('createItem failed:', error);
    toast.error({ title: 'Failed to create item' });
  },
});

// WRONG - Error silently caught, user has no idea
const [createItem] = useCreateItemMutation({
  onError: (error) => {
    console.error(error); // User sees nothing!
  },
});

Error State Component Pattern

interface ErrorStateProps {
  error: Error;
  onRetry?: () => void;
  title?: string;
}

const ErrorState = ({ error, onRetry, title }: ErrorStateProps) => (
  <div className="error-state">
    <Icon name="exclamation-circle" />
    <h3>{title ?? 'Something went wrong'}</h3>
    <p>{error.message}</p>
    {onRetry && (
      <Button onClick={onRetry}>Try Again</Button>
    )}
  </div>
);

Button State Patterns

Button Loading State

<Button
  onClick={handleSubmit}
  isLoading={isSubmitting}
  disabled={!isValid || isSubmitting}
>
  Submit
</Button>

Disable During Operations

CRITICAL: Always disable triggers during async operations.

// CORRECT - Button disabled while loading
<Button
  disabled={isSubmitting}
  isLoading={isSubmitting}
  onClick={handleSubmit}
>
  Submit
</Button>

// WRONG - User can tap multiple times
<Button onClick={handleSubmit}>
  {isSubmitting ? 'Submitting...' : 'Submit'}
</Button>

Empty States

Empty State Requirements

Every list/collection MUST have an empty state:

// WRONG - No empty state
return <FlatList data={items} />;

// CORRECT - Explicit empty state
return (
  <FlatList
    data={items}
    ListEmptyComponent={<EmptyState />}
  />
);

Contextual Empty States

// Search with no results
<EmptyState
  icon="search"
  title="No results found"
  description="Try different search terms"
/>

// List with no items yet
<EmptyState
  icon="plus-circle"
  title="No items yet"
  description="Create your first item"
  action={{ label: 'Create Item', onClick: handleCreate }}
/>

Form Submission Pattern

const MyForm = () => {
  const [submit, { loading }] = useSubmitMutation({
    onCompleted: handleSuccess,
    onError: handleError,
  });

  const handleSubmit = async () => {
    if (!isValid) {
      toast.error({ title: 'Please fix errors' });
      return;
    }
    await submit({ variables: { input: values } });
  };

  return (
    <form>
      <Input
        value={values.name}
        onChange={handleChange('name')}
        error={touched.name ? errors.name : undefined}
      />
      <Button
        type="submit"
        onClick={handleSubmit}
        disabled={!isValid || loading}
        isLoading={loading}
      >
        Submit
      </Button>
    </form>
  );
};

Anti-Patterns

Loading States

// WRONG - Spinner when data exists (causes flash)
if (loading) return <Spinner />;

// CORRECT - Only show loading without data
if (loading && !data) return <Spinner />;

Error Handling

// WRONG - Error swallowed
try {
  await mutation();
} catch (e) {
  console.log(e); // User has no idea!
}

// CORRECT - Error surfaced
onError: (error) => {
  console.error('operation failed:', error);
  toast.error({ title: 'Operation failed' });
}

Button States

// WRONG - Button not disabled during submission
<Button onClick={submit}>Submit</Button>

// CORRECT - Disabled and shows loading
<Button onClick={submit} disabled={loading} isLoading={loading}>
  Submit
</Button>

Checklist

Before completing any UI component:

UI States:

• Error state handled and shown to user
• Loading state shown only when no data exists
• Empty state provided for collections
• Buttons disabled during async operations
• Buttons show loading indicator when appropriate

Data & Mutations:

• Mutations have onError handler
• All user actions have feedback (toast/visual)

Integration with Other Skills

• graphql-schema: Use mutation patterns with proper error handling
• testing-patterns: Test all UI states (loading, error, empty, success)
• formik-patterns: Apply form submission patterns

Limitations

• Use this skill only when the task clearly matches its upstream source and local project context.
• Verify commands, generated code, dependencies, credentials, and external service behavior before applying changes.
• Do not treat examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions.