create-nova-expo-template
Version:
A template for creating a new React Native app using Expo and TypeScript, with a focus on performance and best practices.
80 lines (55 loc) • 1.95 kB
Markdown
# React 19
React 19 is included in Expo SDK 54. This release simplifies several common patterns.
## Context Changes
### useContext → use
The `use` hook replaces `useContext`:
```tsx
// Before (React 18)
import { useContext } from "react";
const value = useContext(MyContext);
// After (React 19)
import { use } from "react";
const value = use(MyContext);
```
- The `use` hook can also read promises, enabling Suspense-based data fetching.
- `use` can be called conditionally, this simplifies components that consume multiple contexts.
### Context.Provider → Context
Context providers no longer need the `.Provider` suffix:
```tsx
// Before (React 18)
<ThemeContext.Provider value={theme}>
{children}
</ThemeContext.Provider>
// After (React 19)
<ThemeContext value={theme}>
{children}
</ThemeContext>
```
## ref as a Prop
### Removing forwardRef
Components can now receive `ref` as a regular prop. `forwardRef` is no longer needed:
```tsx
// Before (React 18)
import { forwardRef } from "react";
const Input = forwardRef<TextInput, Props>((props, ref) => {
return <TextInput ref={ref} {...props} />;
});
// After (React 19)
function Input({ ref, ...props }: Props & { ref?: React.Ref<TextInput> }) {
return <TextInput ref={ref} {...props} />;
}
```
### Migration Steps
1. Remove `forwardRef` wrapper
2. Add `ref` to the props destructuring
3. Update the type to include `ref?: React.Ref<T>`
## Other React 19 Features
- **Actions** — Functions that handle async transitions
- **useOptimistic** — Optimistic UI updates
- **useFormStatus** — Form submission state (web)
- **Document Metadata** — Native `<title>` and `<meta>` support (web)
## Cleanup Checklist
When upgrading to SDK 54:
- [ ] Replace `useContext` with `use`
- [ ] Remove `.Provider` from Context components
- [ ] Remove `forwardRef` wrappers, use `ref` prop instead