ruby on rails - No numeric index needed when saving nested attributes of a resource? -

i have parent model, , child model. i'm trying make form creating parent , associated children @ same time.

in form, have button "add" new child (a parent can have many children user defines). when button clicked, adds hidden field child form , sets name attribute default saved when form submitted. i've been doing adding hidden_field_tag form on button click event:

hidden_field_tag "parent[children_attributes][][name]", "something" 

which creates:

<input id="children_attributes__name" name="parent[children_attributes][][name]" type="hidden" value="something"> 

this seems work! concerned empty []. i'm not sure or why works, discovered does. safe use?

when @ form fields created using fields_for, see sets numeric index middle array/hash (whatever is), so:

<input id="children_attributes_0_name" name="parent[children_attributes][0][name]" type="text"> 

unfortunately, can't use fields_for because have add hidden fields when "add" button clicked.

what's right approach here?

your second question "what's right approach here?"

i use ryan bate's nested form. sorts kind of stuff out you.

your first question "is safe use?"

i dont know. if ever have manually, make sure unique value in [].

the gem believe uses timestamp keep unique.