输入自动完成或Rails中的新功能

I have a simple doubt. I'm working on ruby on rails 5, and I have a relation where the parent is 'category' and the child is 'phrase'. My user can create phrases but I don't want a separate form to create categories, which is just an id and a name. I want in the form for phrases an input where the user can type a category and an autocomplete will pop up with the avaliable options, but if he wants a new one, he simply types it and it will create a new one when he saves the form.I have a simple doubt. I'm working on ruby on r