问rails助手html5

EN

<%= form_for(:description, url:{action:'create'}) do |f| %>
    <div class="row">
      <div class="input-field col s6">
        <%= f.text_field :position, data-length:30 %> 
        <label for="position">Position</label>
      </div> 
   </div>
<% end %>

我犯了个错误，

语法错误，意外的Rails/Projects/free-lance/dressing-shop/app/views/products/new.html.erb:39: keyword_do_block d=( f.text_field :f.text_field，do数据长度:30 );@output_buf ^/home/whitehat/Documents/Books/whitehat/Ruby keyword_do_block语法错误，意外tSYMBEG，期望keyword_do或'{‘或(’ld :位置，做数据长度:30 );@output_buffer.safe_appen ^