Custom meta fields for specific custom type only

I’ve got a custom post type curiculum and a metabox that saves a value to a custom field. However this custom field is added to another custom post type (created by an e-commerce plugin) wpsc-product.

This is a snippet of the code that deals with the metabox. The question is, how to prevent the custom field being added to the wpsc-product?

/* Curiculum Date Metabox */
function curiculum_date_fields() {
if ( get_post_type() == 'curiculum'):
    global $post;
    $custom = get_post_custom( $post->ID );
    $curiculum_date_from = $custom["curiculum_date_from"][0];
    ?>
    <p>
        <label for="curiculum_date_from">Date:</label><br />
        <input size="32" type="text" name="curiculum_date_from" id="curiculum_date_from" value="<?php echo $curiculum_date_from; ?>" />
<?php
endif;
}

function add_curiculum_date_box() {
    add_meta_box("curiculum_date_info", "Event Date", "curiculum_date_fields", "curiculum", "side");
}

function save_curiculum_date() {
    global $post;
    update_post_meta($post->ID, "curiculum_date_from", $_POST["curiculum_date_from"]);
}
add_action('admin_init', 'add_curiculum_date_box');
add_action('save_post', 'save_curiculum_date');
add_action('publish_post', 'save_curiculum_date');

EDIT: Code for the curiculum custom post type:

add_action('init', 'curiculum_register');

function curiculum_register() {

$labels = array(
    'name' => _x('CV Events', 'post type general name'),
    'singular_name' => _x('CV Event', 'post type singular name'),
    'add_new' => _x('Add New', 'testimonials item'),
    'add_new_item' => __('Add New Event'),
    'edit_item' => __('Edit Event'),
    'new_item' => __('New Event'),
    'view_item' => __('View Event'),
    'search_items' => __('Search Events'),
    'not_found' =>  __('Nothing found'),
    'not_found_in_trash' => __('Nothing found in Trash'),
    'parent_item_colon' => ''
);

$args = array(
    'labels' => $labels,
    'public' => true,
    'publicly_queryable' => true,
    'show_ui' => true,
    'query_var' => true,
    'rewrite' => true,
    'capability_type' => 'post',
    'hierarchical' => false,
    'menu_position' => 7,
    'exclude_from_search' => true,
    'supports' => array('title','editor', 'custom-fields')
      );

    register_post_type( 'curiculum' , $args );
 }

Solutions Collecting From Web of "Custom meta fields for specific custom type only"

EDIT: I also recommand you to use nonces to check your field before saving.

EDIT2: Nonces

Just before field, define a nonce :

wp_nonce_field( 'curiculum_meta_box_nonce', 'meta_box_nonce' );

Your saving function is not correct, use this instead :

  function save_curiculum_date($postid) {
    //stop if autosave
    if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;

    // if our nonce isn't there, or we can't verify it, stop
    if( !isset( $_POST['meta_box_nonce'] ) || !wp_verify_nonce( $_POST['meta_box_nonce'], 'curiculum_meta_box_nonce' ) ) return;

    // if our current user can't edit this post, stop
    if( !current_user_can( 'edit_post' ) ) return;

update_post_meta($postid, "curiculum_date_from", $_POST["curiculum_date_from"]);
}

The fields function is not correct, use this instead :

$curiculum_date_from = get_post_meta(get_the_ID(),'curiculum_date_from',true);
?>
<p>
    <label for="curiculum_date_from">Date:</label><br />
    <input size="32" type="text" name="curiculum_date_from" id="curiculum_date_from" value="<?php echo $curiculum_date_from; ?>" />

After removing the action:

add_action('admin_init', 'add_curiculum_date_box');

You can try this:

function add_curiculum_date_box($post){
      add_meta_box(
        "curriculum_date_info", 
        "Event Date", 
        "curiculum_date_fields", 
        $post->post_type,
        "side"
      );
}

And add this to your CPT $args:

'register_meta_box_cb' => 'add_curiculum_date_box'

When this post type is registered, it also sets into motion events that will create the meta box in the appropriate write screen. It saves the trouble of having to use a separate call to add_action to set up the meta box. It also keeps all of the code for the individual post type in one place. Functionally, it does the exact same thing as the “add_meta_boxes” variable hook. It is just a different way to accomplish the same task.

Credits

just in case you didn’t manage to find a simple but elegant fix for this, or if anybody else has stumbled upon this (or a similar issue), with WordPress Creation Kit from wordpress.org users can easily create CPT’s or add meta-boxes them (if in any doubt, feel free to read the description of the plugin).