> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ollie.shop/llms.txt
> Use this file to discover all available pages before exploring further.

# useCheckoutSession

The `useCheckoutSession` hook provides access to the current checkout session data and functionality to update it. It gives you access to both the parsed, platform-agnostic checkout session data and the raw session data from the e-commerce platform.

## **Import**

```typescript theme={"system"}
import { useCheckoutSession } from '@ollie-shop/sdk';
```

## **Usage**

```typescript theme={"system"}
const { session, rawSession, updateSession, sessionValidity } = useCheckoutSession();

// Access session data
console.log(session.cartItems);

// Update session data
updateSession(newSession, newRawSession);

// Check if the session is valid
if (sessionValidity?.valid) {
  // Session is valid
} else {
  // Handle validation errors
  console.error(sessionValidity?.errors);
}
```

## **Return Value**

Returns an object with:

* `session: CheckoutSession<Extensions>` - The parsed, platform-agnostic checkout session conforming to your custom schema
* `rawSession: unknown` - The original session data from the e-commerce platform (VTEX, Shopify, etc.) in raw/unparsed form
* `updateSession: (session: CheckoutSession<Extensions>, rawSession: unknown) => void` - Function to update both the parsed and raw session data
* `sessionValidity?: ValidationSuccess | ValidationFailure` - Results from the last validation check of the session data

## **Session Validation**

The `sessionValidity` object contains the results of validating the checkout session against a ZodSchema. This schema-based validation ensures that all required data is present and formatted correctly.

```typescript theme={"system"}
if (sessionValidity?.valid) {
  // Session is valid - all required fields are present and correctly formatted
} else {
  // Session is invalid - access validation errors
  const errors = sessionValidity?.errors;
}
```

### **Understanding sessionValidity**

* `sessionValidity` uses a ZodSchema to validate the structure and content of your checkout session
* It helps identify missing or invalid information in customer details, shipping addresses, payment methods, etc.
* This validation is crucial for determining whether a user can proceed to checkout or needs to provide more information

### **Validating Address Information**

A common use case is checking if some information is complete before redirecting the user to the next step

```typescript theme={"system"}
export const function PageShipping {
  const { sessionValidity } = useCheckoutSession();

  // Extract address validation errors if they exist
  const missingAddressFields =
    sessionValidity && "errors" in sessionValidity
      ? sessionValidity.errors?.shipping?.addresses
      : undefined;

  // Component rendering...
  return (
    <form onSubmit={() => {}}>
        <button type="submit">
            Next to {missingAddressFields ? 'address' : 'payment'}
        </button>
    </form>
  )
}
```

This pattern lets you detect missing required fields and direct users to the appropriate step in your checkout flow to provide that information.

## **Example**

```typescript theme={"system"}
import { useCheckoutSession } from '@ollie-shop/sdk';

function CartSummary() {
  const { session } = useCheckoutSession();

  return (
    <div>
      <h2>Cart Summary</h2>
      <p>Total Items: {session.cartItems.length}</p>
      <p>Subtotal: ${session.totals.items}</p>
      {(session.totals.discounts ?? 0) > 0 && (
        <p>Discounts: -${session.totals.discounts}</p>
      )}
      <p>Shipping: ${session.totals.shipping ?? 0}</p>
      <p><strong>Total: ${session.totals.total}</strong></p>
    </div>
  );
}
```

## **Notes**

* Use type parameters with `useCheckoutSession<YourExtensions>()` when you have custom properties in your checkout session