You can search entire cart and checks if it contains only one product of a particular category.
Here suppose your category slug is 'your-category-slug'
Here is a simple function you can place this in your plugin or theme function file
function check_category_alone_in_cart( $category ) {
// check each cart item for our category
foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
// if a product is not in our category, bail out since we know the category is not alone
if ( ! has_term( $category, 'product_cat', $cart_item['data']->id ) ) {
return false;
}
}
// if we're here, all items in the cart are in our category
return true;
}
function chk_wc_prevent_checkout_for_category() {
// If the cart is empty, then let's hit the ejector seat
if (WC()->cart->is_empty()) {
return;
}
// set the slug of the category for which we disallow checkout
$category = 'your-category-slug';
// get the product category
$product_cat = get_term_by( 'slug', $category, 'product_cat' );
// sanity check to prevent fatals if the term doesn't exist
if ( is_wp_error( $product_cat ) ) {
return;
}
// check if this category is the only thing in the cart
if ( check_category_alone_in_cart( $category ) ) {
// render a notice to explain why checkout is blocked
wc_add_notice( 'Cart contains the product which has category "your-category-slug" !!! ', 'error' );
return false;
}
return true;
}
add_action( 'woocommerce_check_cart_items', 'chk_wc_prevent_checkout_for_category' );
