cannot filter after using pre_get_posts

The problem is that you always set the meta query, if you don’t want it to apply in a particular situation, you need to check for that situation and account for it. Similar to how you’re already checking with is_admin, or is_main_query, etc.

In this situation, you’ll want to check the $_GET parameters to detect if the filter has been applied on the posts screen, and only set the meta query if it isn’t present. In this case, I believe the parameter used is m, but there are several others in the URL to check against

Further notes:

  • When you get the filter working, you probably won’t see the results you’re expecting as that filter works on the publish date. If you’re expecting to see applications filtered by date, you’ll need to detect when a filter is happening and add a different meta query that queries app_date via those filter arguments, then undoes the default filter
  • Filtering posts via their post meta is expensive! Really, really expensive! Treat these as a rare thing you only do occasionally. I’ve seen major sites brought down by simple post meta queries, it puts a big strain on the database. That’s why taxonomy tables were created, otherwise, categories and tags would be stored in post meta. If you can repurpose the publish date, that’ll make a huge difference.
  • You’re not using a standardised format for your date values. Not only that but they’re ambiguous! Use YYY-MM-DD instead and follow the ISO standards agreed upon, and you’ll get better compatibility
  • Consider specifying that your values are dates using 'type' => 'DATE'
  • You can make the function easier to read and modify by separating out those conditionals into guards and exiting early, e.g. if ( !is_admin() ){ return; }, this also makes debugging easier, and lets you test each check individually if things go wrong

There is also a bug in your code, that is unrelated to your issue, but still a bug. The code checks if the current query is for a particular post type, but because it uses an assignment operator = instead of a comparison operator ==, instead of checking if they match, it sets/assigns the value. As a result, all queries are now queries for apps. This is unrelated to the issue in your question.

Related Posts:

  1. Modify query in pre_get_posts action is messing up my nav menu
  2. remove_action or remove_filter with external classes?
  3. Why does save_post action fire when creating a new post?
  4. Difference between do_action_ref_array() and do_action()
  5. Why is there both a save_post and wp_insert_post action?
  6. When is admin_init Action ran?
  7. Can an action callback prevent the parent from continuing execution?
  8. How do I enqueue a script to run inside the Gutenberg editor?
  9. How can I find out what functions are assigned to actions?
  10. Disable WooCommerce action
  11. How can I remove the WP menu from the admin bar?
  12. How to show more posts on an archive page?
  13. add_action customize_register not working
  14. Passing arguments into ‘init’ function
  15. How to use conditional add_action for WordPress
  16. WP Schedule Event – Every Day When First Visitor Comes
  17. How to remove an action that is added inside a class
  18. add action which returns modified value
  19. WordPress admin WP_table_list show incorrectly
  20. How to add a checkbox inside the “Publish post” widget?
  21. What’s the usage of action do_meta_boxes?
  22. Custom bulk actions in WP 3.7.1
  23. Remove action from a plugin class
  24. pre get posts changing the query
  25. Exclude trash from save_post
  26. How to check if an action is already fired?
  27. add_action and wp_head not display content in head section
  28. use add_action(‘wp_head’) in a widget
  29. array of objects to do_action, callback gets singular object?
  30. Preventing frontpage to be deleted/moved to trash
  31. Selectively applying action based on role
  32. How to remove a custom action on child theme?
  33. Action hook on only publishing post not on editing or updating
  34. Performance : Duplicating `add_action`
  35. add_action in class and use it in theme
  36. How to track post number on the_loop
  37. Better action hook for creating table than after_switch_theme and switch_theme action hook
  38. Adding the hook ‘vc_before_init’ inside a object
  39. $GLOBALS[‘hook_suffix’] variable empty
  40. How to apply action the_post to the post that is only being mainly displayed
  41. admin_notices on runtime in function
  42. Using several add_action with parameters inside a class
  43. Action hook load_textdomain $domain variable
  44. Action hook for editing post
  45. add_action and do_action: multiple calls to same callback?
  46. remove_action returns false regardless of priority
  47. Set a custom display_name on user_register?
  48. How to make an action run in the background?
  49. WP cron doesn’t pass through my arguments
  50. how to add submenu item under parent menu item with code
  51. Why does my wp_safe_redirect output the ERR_TOO_MANY_REDIRECTS error?
  52. Re-order Woocommerce single product and echo div around moved & duplicated Woocommerce hooks
  53. Custom Post type forgetting data
  54. How to call a static function in add_action() inside another static function?
  55. Insert custom postmeta when custom post type published
  56. Call do_action class’s function
  57. Generate payment URL in custom email [closed]
  58. Can’t Get Metabox Data Saved Assistance Needed
  59. missing argument 2 when passing arguments to add_action
  60. is there an update_post_meta action
  61. comment_post callback function: how to run it in the background.
  62. Add new users to “add new user” page on admin’s dashboard
  63. Run a function on all posts
  64. Remove an action added within a class in a WordPress plugin
  65. add_action( ‘publish_pelicula’, ‘post_published_notification’, 10, 2 ); does not trigger propperly
  66. WP_Query – How to get all posts of specific days of week by custom field date?
  67. Filter WooCommerce archive pages by an additional category
  68. Change Post Publish Date to Post Modified Date in All Places
  69. save_post not triggered when a post is updated
  70. Action ‘init’ function doesn’t return variable
  71. add_action to wp_head is added, but not called
  72. Where to place add_action when enqueueing?
  73. Insert Google authorship into WordPress header
  74. add_action before theme setup
  75. How can I get the user that publishes a post?
  76. add_action which contains first argument admin_print_scripts-$page
  77. update_user_meta not updating
  78. How do i know which action / filters are called when i call get_option()
  79. How can I get more out of `$post` in an `add_action` callback?
  80. Add Tag to post after publishing
  81. Remove action not working in child theme
  82. Call to Action Button – Resize Help [closed]
  83. How do I dequeue js/css at the last possible moment?
  84. Translate are not working for standard admin
  85. wpdb->insert creates duplicate rows
  86. add_action init breaks site on PHP 7.1
  87. Need data from two different actions
  88. Adding add_action function
  89. action future_post returns wrong date
  90. XML Imported Custom Posts
  91. Hook into admin_notices after sending mail
  92. save_post action not firing when save
  93. WooCommerce wp_insert_post action firing on every save
  94. WordPress’ work or execution flow manipulating $wpdb
  95. Add-action in function
  96. Building WP Web App: Creating a Feed for post revisions
  97. Can admin_bar_menu or another action be used to modify the admin bar on the admin side?
  98. What is the first action or filter executed by wordpress?
  99. Using add action for class with construct
  100. Webhook: save_post action fires wp_remote_post twice