Rails 4 - Simple form arguments - ruby-on-rails

Question

Can anyone see what's wrong with this form of expression?
<%= simple_fields_for :article do |f| %>
<%=f.input :q, :nil, placeholder: "Search" %>
<% end %>
Error message says:
wrong number of arguments (3 for 1..2)
So- my wider code is:
articles#index.html.erb:
<div class="row">
<div class="col-md-10 col-md-offset-1">
<%= render 'articles/searchform' %>
</div>
<div class="col-md-10 col-md-offset-1">
<% Article.all.sort_by(&:created_at).in_groups_of(3) do |group| %>
</div>
<div class="row">
<% group.compact.each do |article| %>
<div class="col-md-4">
<div class="indexdisplay">
<%= image_tag article.image_url, width: '100%', height:
'200px' if article.image.present? %>
<div class="indexheading"> <%= link_to article.title, article %> </div>
<div class="indexsubtext"> <%= truncate(article.body, :ommission =>
"...", :length => 250) %></div>
</div>
</div>
<% end %>
</div>
<div class="row">
<%= link_to 'New Article', new_article_path %>
</div>
In my views articles#form.html.erb
<div class="col-xs-10 col-xs-offset-1">
<%= simple_form_for(#article) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :title, autofocus: true %>
<%= f.input :body, :label => "Post", :input_html => {:rows => 10} %>
<%= f.input :image, :label => "Add an image" %>
</div>
<div class="form-actions">
<%= f.button :submit, "Review a draft", :class =>
'formsubmit' %>
</div>
<% end %>
In articles#searchform.html.erb
<% f.simple_fields_for :article do |a| %>
<%=a.input :q, :nil, placeholder: "Search" %>
<% end %>
I get this error:
undefined local variable or method `f' for #<#<Class:0x007f874133c410>:0x007f8740448058>

Answer 1

You are missing your form variable, e.g. f.
For instance if you have simple_form_for ... do |f| you should then write
= f.simple_fields_for :article do |article|
= article.input :q, :nil, placeholder: 'search'
[EDIT] You seem confused. The simple_fields_for is a special command to iterate over nested items, inside a form (e.g. comments for a post). So simple_fields_for would require a surrounding form (simple_form_for). For your search-form you should just be using simple_form_for.