ruby - Rails - two attributes one input field

i need html output form

 <input class="text valid" id="contacts_custom_field_phone_number_50754" name="contacts[custom_field][phone_number_50754]" size="30" type="text">

this got far

= f.label "phone" %br     = f.text_field :custom_field=>{:phone_number_50754=>"123-213-2134"}

this wrong works in rails console , posts data api

how write code output need?

when in rails console

  :custom_field=>{:phone_number_50754=>"123-123-2134"}

it posts api

you can use fields_for:

- f.fields_for :custom_field |custom_fields|   = custom_fields.text_field :phone_number_50754

Shashtri