NoMethodError in Discussions#show - ruby-on-rails

Question

Below is code extract from my file app/views/discussions/show.html.erb where line 16 raised this error:
undefined method `markdown' for #<#<Class:0x000000000c94e0d8>:0x000000000c94c6e8>
s<div class="columns">
<div class="column is-8">
<h1 class="title is-2 has-text-grey discussion-title"><%= #discussion.title %></h1>
<h3 class="subtitle is-5 has-text-grey-lighter">by <%= #discussion.user.username %> in <%= link_to #discussion.channel.channel, #discussion.channel %></h3>
<div class="level">
<div class="level-left"></div>
<div class="level-right">
<% if discussion_url(#discussion) %>
<div class="buttons">
<%= link_to 'Edit Discussion', edit_discussion_path(#discussion), class:'button'%>
<%= link_to 'Delete', discussion_path(#discussion), method: :delete, data: { confirm: "Delete discussion?" }, class:'button' %>
</div>
<% end %>
</div>
</div>
<div class="content"><%= markdown (#discussion.content) %></div>
<!-- ^^^^^^^^ -->
<h2 class="subtitle is-5 has-text-grey"><%= #discussion.replies.count %> Replies</h2>
<div id="discussion-replies">
<%= render #discussion.replies %>
</div>
<hr/>
<h3 class="subtitle is-3 has-text-grey">Leave a reply</h3>
<% if user_signed_in? %>
<%= render 'replies/form' %>
<% else %>
<p>To reply you need to <%= link_to 'login', new_user_session_path %>. Don't have an account?
<%= link_to 'Sign up', new_user_registration_path %> for one.</p>
<% end %>
</div>
<%= render 'sidebar' %>
</div>
cant view reply or comment section

Answer 1

Rails doesn't include a markdown method. You'll have to use a gem, write something yourself or a combination of the two. You could for example use the redcarpet gem, or one of the other markup processor gems.
Then write your own helper using this using this gem.
# app/helpers/markdown_helper.rb
module MarkdownHelper
MARKDOWN = Redcarpet::Markdown.new(Redcarpet::Render::HTML)
def markdown(markdown_string)
MARKDOWN.render(markdown_string).html_safe
end
end
For usage and possible render configurations checkout out the redcarpet documentation.
With this helper present you can simply do the following in the view:
<%= markdown(#discussion.content) %>