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AbstractFlow implements FlowInterface and provides all the boilerplate so you can focus on your flow’s unique logic. Extend it and implement the three abstract methods. 
namespace UTB\ProductBuilder\Flows;

abstract class AbstractFlow implements FlowInterface
{
    // ...
}

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Extending AbstractFlow

use UTB\ProductBuilder\Flows\AbstractFlow;

class MyFlow extends AbstractFlow
{
    public function get_id(): string        { return 'my_flow'; }
    public function get_name(): string      { return 'My Flow'; }
    public function get_description(): string { return 'Does something custom.'; }
    public function get_icon(): string      { return 'dashicons-star-filled'; }

    public function get_shortcodes(): array { return ['my_flow_form' => 'render_custom_content']; }
    public function get_ajax_endpoints(): array { return []; }

    // The three required methods:
    protected function render_custom_content(): void { /* output HTML */ }
    public function prepare_cart_metadata(array $post_data): array { return []; }
    public function validate_cart_data(array $post_data) { return true; }
}

​
Methods you MUST override

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render_custom_content(): void

Outputs the HTML for the product page. Called by render_flow_wrapper(), which wraps the output in <div class="utb-product-flow-container id-{flow_id}">. 
protected abstract function render_custom_content(): void;

​
prepare_cart_metadata(array $post_data): array

Builds the metadata array saved to the WooCommerce cart item and order. See FlowInterface::prepare_cart_metadata() for full documentation. 
public abstract function prepare_cart_metadata(array $post_data): array;

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validate_cart_data(array $post_data)

Validates the add-to-cart form submission. Return true on success or an error string on failure. See FlowInterface::validate_cart_data() for full documentation. 
public abstract function validate_cart_data(array $post_data);

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Methods you CAN override

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enqueue_assets(): void

Called on wp_enqueue_scripts. The base implementation checks is_product() and applies_to_product() and returns early if neither applies. Override to enqueue flow-specific JavaScript and CSS. 
public function enqueue_assets(): void
{
    // Base class exits early if not on a matching product page.
    // Override to call wp_enqueue_script() / wp_enqueue_style().
}

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get_shortcodes(): array

Returns shortcodes to register. Defaults to an empty array in the base class (the interface requires it; AbstractFlow does not provide a default). Override to register shortcodes.

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get_ajax_endpoints(): array

Returns AJAX endpoints to register. Both wp_ajax_{action} and wp_ajax_nopriv_{action} are registered for each entry, so all endpoints are accessible to logged-in and guest users. Override to add endpoints.

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Hooks registered by init()

Calling AbstractFlow::init() (which happens automatically via FlowRegistry) registers these WordPress/WooCommerce hooks:
HookMethodPriorityArgs
wpmaybe_setup_landing50—
woocommerce_add_to_cart_validationvalidate_add_to_cart103
woocommerce_add_cart_item_dataadd_cart_item_data_filter103
woocommerce_before_calculate_totalsapply_dynamic_pricing201
woocommerce_checkout_create_order_line_itemsave_order_item_meta104
wp_enqueue_scriptsenqueue_assets——
Shortcodes are registered with add_shortcode() and AJAX endpoints with add_action() during init() based on what your overridden get_shortcodes() and get_ajax_endpoints() return.

​
Product landing cleanup

When applies_to_product() returns true for the current product, setup_product_landing() removes the following WooCommerce elements to make room for the flow’s custom UI: Removed from woocommerce_before_main_content:
  • woocommerce_breadcrumb (priority 20)
Removed from woocommerce_sidebar:
  • woocommerce_get_sidebar (priority 10)
Removed from woocommerce_single_product_summary:
  • woocommerce_template_single_title (priority 5)
  • woocommerce_template_single_rating (priority 10)
  • woocommerce_template_single_price (priority 10)
  • woocommerce_template_single_excerpt (priority 20)
  • woocommerce_template_single_add_to_cart (priority 30)
  • woocommerce_template_single_meta (priority 40)
  • woocommerce_template_single_sharing (priority 50)
Removed from woocommerce_after_single_product_summary:
  • woocommerce_output_product_data_tabs (priority 10)
  • woocommerce_upsell_display (priority 15)
  • woocommerce_output_related_products (priority 20)
After removing standard elements, the method injects the flow wrapper into woocommerce_single_product_summary at priority 30 and applies inline CSS to hide any price markup that the theme may still render.

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Utility methods

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Nonce helpers

protected function create_nonce(string $action): string
Creates a WordPress nonce scoped to this flow. The nonce action is "{flow_id}_{action}". 
protected function verify_nonce(string $nonce, string $action): bool
Verifies a nonce created by create_nonce(). Returns true if valid.

​
AJAX response helpers

protected function ajax_success($data = []): void
Sends a JSON success response via wp_send_json_success() and terminates. 
protected function ajax_error(string $message, $data = [], int $status_code = 400): void
Sends a JSON error response via wp_send_json_error() with the given HTTP status code and terminates. The $data parameter is merged into the response body alongside the message key.

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Sanitization helpers

protected function sanitize_text($value): string
Runs wp_unslash() then sanitize_text_field() on $value. 
protected function sanitize_email_field($value): string
Runs wp_unslash() then sanitize_email() on $value. 
protected function sanitize_int($value): int
Casts $value to int.

​
Example: minimal custom flow

use UTB\ProductBuilder\Flows\AbstractFlow;

class WorkshopFlow extends AbstractFlow
{
    public function get_id(): string        { return 'workshop_flow'; }
    public function get_name(): string      { return 'Workshop Enrollment'; }
    public function get_description(): string { return 'Enrolls students in workshops.'; }
    public function get_icon(): string      { return 'dashicons-groups'; }

    public function get_shortcodes(): array
    {
        return ['workshop_form' => 'render_custom_content'];
    }

    public function get_ajax_endpoints(): array
    {
        return ['workshop_get_slots' => 'handle_get_slots'];
    }

    protected function render_custom_content(): void
    {
        echo '<form id="workshop-form" method="post">';
        wp_nonce_field($this->create_nonce('add_cart'));
        echo '<button type="submit">Enroll</button></form>';
    }

    public function validate_cart_data(array $post_data)
    {
        if (!$this->verify_nonce($post_data['_wpnonce'] ?? '', 'add_cart')) {
            return 'Security check failed.';
        }
        return true;
    }

    public function prepare_cart_metadata(array $post_data): array
    {
        return [
            '_utb_form_data' => json_encode(['source' => 'workshop_form']),
        ];
    }

    public function handle_get_slots(): void
    {
        $this->ajax_success(['slots' => 12]);
    }
}

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