custom field value as shortcode parameter

Question

i am using a plugin (download monitor) to display downloads via shortcodes. the shortcode has a single parameter, which is the download's ID: [download id="123"]

i'd like to be able to modify the download ID parameter within the shortcode via a custom field value.

i've created a custom field - ur-single-form-id - and also a shortcode for it [ur_single_form_id] via the following function:

function ur_single_form_id() {
    $cf = get_post_meta( get_the_ID(), 'ur-single-form-id', true );
    $var = '<p class="your-class">' . $cf . '</p>';
    return $var;
}
add_shortcode( 'ur_single_form_id', 'ur_single_form_id' )

this was in the hopes of being able to do something like this: [download id="[ur_single_form_id]"]

unfortunately things aren't parsed as expected, and i get an error saying "download not found".

how can i implement this such that the download ID is populated within the download monitor shortcode using the custom field value?

thanks

Answer 1

I never worked with this plugin, just downloaded it from repository and found that they provide a filter for id value.

Add this filter callback function to your functions.php file.
[download id="auto"] - will use id from your post meta (hardcoded meta name)
[download id="123"] - will use id 123

function download_shortcode_custom_id($id, $atts = []){
     if(!is_numeric($id) && $id = 'auto' ):
        //change 'temp' post meta name with your own
        $post_meta = get_post_meta(get_queried_object_id(), 'temp', true);
        $post_meta ? $id = $post_meta : null;
     endif;
     return $id;
}

add_filter('dlm_shortcode_download_id', 'download_shortcode_custom_id', 10, 2);

As a second option you can set your post meta name as id value
[download id="temp"] - will use this post meta name to retrieve an id
[download id="123"] - will use id 123

function download_shortcode_custom_id($id, $atts = []){
     if( !is_numeric($id) ):
        $post_meta = get_post_meta(get_queried_object_id(), $id, true);
        $post_meta ? $id = $post_meta : null;
     endif;
     return $id;
}

add_filter('dlm_shortcode_download_id', 'download_shortcode_custom_id', 10, 2);