Specify FolderId When Uploading a File on the Frontend

Question

In a front-end form where I am uploading a file, I need to specify a specific subfolder. I can't do it in the cp dynamic field for reasons so I was hoping to use a hidden field to set the folderId. The folderId exists and each entry has a different folder. I have this code that works but I can't figure out the code, for example something like: folderId: 44

<form method="post">
 {{ csrfInput() }}
 {{ actionInput('entries/save-entry') }}
 {{ hiddenInput('sectionId', '3') }}
 {{ hiddenInput('enabled', '1') }}
 {{ hiddenInput('entryId', entry.id) }}
 {{ hiddenInput('redirect', craft.app.request.absoluteUrl|hash) }}

    {% for relatedAssetId in entry.patientFiles.ids() %}
      {{ input(
          'hidden',
          'fields[patientFiles][]',
          relatedAssetId,
        ) }}
    {% endfor %}
          {{ input('file', 'fields[patientFiles][]', options={
             multiple: true,
          }) }}
    <button class="btn btn-primary" type="submit">Upload</button>

Answer 1

You can find a specific folder using the Assets service:

https://docs.craftcms.com/api/v3/craft-services-assets.html#public-methods

If you know all the necessary information when that template is parsed, the findFolder method might be useful but ensureFolderByFullPathAndVolume is probably more precise.

For example:

{{ hiddenInput( 'secret_folder_id', 
    craft.app.assets.ensureFolderByFullPathAndVolume($volumePath, $assetVolume) ) }}