In AEM 6.2 how to make image alt text field mandatory based on image field - aem

Question

I have two fields in dialog, image field and image alt text field. My requirement is to make the "image alt text" field mandatory if image is authored. But if image is not authored, then "image alt text" should not be mandatory.
how can we achieve in AEM 6.2 touch ui?
<image
jcr:primaryType="nt:unstructured"
sling:resourceType="granite/ui/components/foundation/form/fileupload"
autoStart="{Boolean}false"
class="cq-droptarget"
fieldDescription=“Authored Image"
fieldLabel="Image"
fileNameParameter="./fileName"
fileReferenceParameter="./fileReference"
mimeTypes="[image]"
multiple="{Boolean}false"
name="./imagedragdrop"
title="Upload Image Asset"
uploadUrl="${suffix.path}"
useHTML5="{Boolean}true"/>
<imageAltText
jcr:primaryType="nt:unstructured"
sling:resourceType="granite/ui/components/foundation/form/textfield"
fieldDescription=“Image alt text"
fieldLabel="Image Alt Text"
name="./imageAltText"/>

Answer 1

Here is a simple way to achieve this:
When the file upload widget is authored, it will have the class is-filled and when it's not authored, it will not have that class.
First:
We need to give both fields a special selector, I'm going with ID's:
Add the property id="file-upload-special" to your file upload dialog widget
Add the property id="alt-special" to your alt text (textfield) widget
Second:
Create a clientlib with the following categories="[cq.authoring.dialog]"
Third:
Add the following js to the clientlib:
// register a validator
$(window).adaptTo("foundation-registry").register("foundation.validation.validator", {
selector: "#alt-special", // validates the specific alt field
validate: function(el) {
var $el = $(el);
var $form = $el.closest('form'); // get the form
var $upload = $form.find('#file-upload-special'); // find the file-upload widget
if($upload.hasClass('is-filled') && !$el.val()){ // if class exists, return validation msg
return 'this field is required';
} else {
return;
}
}
});
now the alt field should only be validated if the file-upload is authored.