How to use placeholders instead of labels in simple_form?

You need 3 steps to enable showing placeholders instead of labels automatically and need to do more configurations.

1. make sure b.use :placeholder in simple_form.rb

2. make sure b.use :input instead of b.use :label_input

3. most important, modify your simple_form.en.yml:

en:   
  simple_form:
    "yes": 'Yes'
    "no": 'No'
    required:
      text: 'required'
      mark: '*'
    placeholders:
      user:
        name: 'name'

in your page:

<%= simple_form_for @user do |f|%>
  <%= f.input :name%>
<% end%>

Every placeholder needs to be defined here, or it will not display.

simple_form lets you hide an individual label by passing in label:false to each input. For example: <%= f.input :email, placeholder: 'Email', label:false %> will hide the label for your email input in a form.