Change Dropdown field to multiselect field according to Category

Question

Hello everyone, 
 
 I have a "Type" field as dropdown and I want to change it multiselect field according to Category change. Please share your idea that how can I do it. 
 If category = specimen then Type field = multiselect. 
 If category = product then Type field = dropdown. 
 
 Thanks 
 Laxmichand saini

Laxmichand Saini · Accepted Answer

Hello Laxmichand Saini , 
 
 I don't think that it's safe to change the field type because the data consistency will be wrong in database. 
 So, in my mind, you need 
 
 a dropdown field, visible if category = specimen 
 a multiselect field, visible if category = product 
 both fields used the same dropdown list 
 a "consolidated" multiselect field where the value is stored (using hook for instance) : so only one value if specimen, possibly many if product
 
 this field will be used for reporting etc.

best regards, 
 Fred

Laxmichand Saini · Answer

You can not modify a field type on the fly, instead you can create a custom field type which extends from enum (the target field must be a multienum) and in its js controller you may decide whether to render additional options or not. Follow the example below: 
 
 If field has a selected option and category is specimen: show all available remaining options 
 If field has a selected option and category is product: do not show any other option 
 If selected option has been removed from field: show all available options 
 
 Regards