Specify parent page template

Question

I don't want to define a template from admin because I have lot of page and so if I change it I might forget my selected template.

So I want make that template in page.

Here is my page structure

Mango (page)

-Orange (parent page)

-- lime (parent page)

For my mango and all parent pages I will use the same template, but I don't want to that by selecting one for each from admin. I want that defined in functions.php or page.php with get_template_part or any other way. For example, if lime/mango/orange or whatever which is under mango page, then get_template_part will use mango so that my template will be mango.php.

Any suggestions to make this work?

i am not sure is that make scene or not

Answer 1

All types of templates have filters to let you control what template is loaded. For pages there's page_template, where you can check the queried page against an ID, or see if the ID exists in an array of a page's ancestor IDs.

function wpd_page_template_filter( $template ){
    // the ID of Mango page
    $parent_page = 20;

    if( $parent_page == get_queried_object_id()
        || in_array( $parent_page, get_ancestors( get_queried_object_id(), 'page' ) ) ){
        $template = locate_template( 'mango.php', false );
    }
    return $template;
}
add_filter( 'page_template', 'wpd_page_template_filter' );