Populate a custom field dropdown with post titles by author

Question

Just getting into wordpress and learning a lot! I know how to create a custom field and use it for basic purposes. I'm trying to do a little more now...I'm hoping someone can help me.

Here is the scenario:

I have businesses and events section on my website. Businesses use the default "posts" from wordpress, "events" are a custom post type.

I want to create a custom field to use for events that populates a dropdown list of the business posts the current user is the author of, effectively linking the two together. This way the user can only see the business posts they've created in the list and can not create events and link them to random businesses.

I've tried utilizing the "LittlePromoBox" class found in this post. But have had no luck...I've tried to understand the logic but its too advanced for me at this point..can anyone help me out?

Answer 1

here: What you need is to create a meta box so first you use the add_meta_box()

// Hook into WordPress add_meta_boxes action
add_action( 'add_meta_boxes', 'add_Businesses_custom_metabox' );

/**
 * Add meta box function
 */
function add_Businesses_custom_metabox() {
    add_meta_box( 'custom-metabox', __( 'Businesses' ), 'Businesses_custom_metabox', 'events', 'side', 'high' );
}

here you can see that i used "events" as the post type i want to register this meta box to and that my callback function is: Businesses_custom_metabox() and its the function that actually displays the metabox, so we define it like this:

/**
 * Display the metabox
 */
function Businesses_custom_metabox($post) {
    global $post,$current_user;
    //remember the current $post object
    $real_post = $post;
    //get curent user info (we need the ID)
    get_currentuserinfo();
    //create nonce
    echo '<input type="hidden" name="Businesses_meta_box_nonce" value="', wp_create_nonce(basename(__FILE__)), '" />';
    //get saved meta
    $selected = get_post_meta( $post->ID, 'a_businesses', true );
    //create a query for all of the user businesses posts
    $Businesses_query = new WP_Query();
    $Businesses_query->query(array(
                            'post_type' => 'posts',
                            'posts_per_page' => -1,
                            'author' => $current_user->ID));
    if ($Businesses_query->have_posts()){
        echo '<select name="a_businesses" id="a_businesses">';
        //loop over all post and add them to the select dropdown
        while ($Businesses_query->have_posts()){
            $Businesses_query->the_post();
            echo '<option value="'.$post->ID.'" ';
            if ( $post->ID == $selected){
                echo 'selected="selected"';
            }
            echo '>'.$post->post_title .'</option>';
        }
        echo '<select>';
    }
    //reset the query and the $post to its real value
    wp_reset_query();
    $post = $real_post;
}

I tried to comment ever bit of it so you can understand better. And the last thing you have to do is process the metabox when a post is saved:

//hook to save the post meta
add_action( 'save_post', 'save_Businesses_custom_metabox' );
/**
 * Process the custom metabox fields
 */
function save_Businesses_custom_metabox( $post_id ) {
    global $post;
    // verify nonce
    if (!wp_verify_nonce($_POST['Businesses_meta_box_nonce'], basename(__FILE__))) {
        return $post_id;
    }
    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return $post_id;
    }
    // check permissions
    if ('events' == $_POST['post_type']) {
        if (!current_user_can('edit_page', $post_id)) {
            return $post_id;
        }
    } elseif (!current_user_can('edit_post', $post_id)) {
        return $post_id;
    }

    if( $_POST ) {
        $old = get_post_meta($post_id, 'a_businesses', true);
        $new = $_POST['a_businesses'];
        if ($new && $new != $old){
            update_post_meta($post_id, 'a_businesses', $new);
        }
    }
}