WordPress adding custom columns to custom post types

functions.php

<?php
// Add the custom columns to the book post type:
add_filter( 'manage_<post_type>_posts_columns', 'set_custom_edit_<post_type>_columns' );
function set_custom_edit_<post_type>_columns($columns) {
    unset( $columns['author'] );
    $columns['column_name'] = __( 'Column name', 'text-domain' );

    return $columns;
}

// Add the data to the custom columns for the <post_type> post type:
add_action( 'manage_<post_type>_posts_custom_column' , 'custom_<post_type>_column', 10, 2 );
function custom_<post_type>_column( $column, $post_id ) {
    switch ( $column ) {
        case 'column_name':{
			// Variables

			echo "TEXT"

            break;
	    }

    }
}