Convert html to text in ROR - ruby-on-rails

Question

HTML
<p>Hello</p>
<p>this is <br></p>
<p>a <br></p>
<p>test message</p><br>
I have already tried 'strip tags' which gives me the following output :
"Hellothis is a test message"
The output I want:
Hello
this is
a
test message

Answer 1

html = "<p>Hello</p>
<p>this is <br></p>
<p>a <br></p>
<p>test message</p><br>"
strip_tags
strip_tags helper seems to work fine :
puts ActionController::Base.helpers.strip_tags(html)
# =>
# Hello
# this is
# a
# test message
Nokogiri
Nokogiri is included by default in Rails, so you could also use :
doc = Nokogiri::HTML(html)
puts doc.xpath("//text()").to_s
It outputs :
Hello
this is
a
test message
Convert newlines to spaces
If you want to remove newlines :
ActionController::Base.helpers.strip_tags(html).gsub(/\s+/,' ')
#=> "Hello this is a test message"

Answer 2

The HTML is rendered by a browser like:
Hello
this is
a
test message
This isn't quite correct though, because the HTML contains trailing <br> tags in the <p> tags, which should be a string like:
this is \n\n\n
which is normally considered a paragraph plus a new-line. But, browsers play games when rendering text in order to make it more readable, and gobble blank lines and spaces. For example, this HTML:
<p>foo</p>
<p></p>
<p></p>
<p></p>
<p>bar</p>
renders as:
foo
bar
and:
<p>foo bar</p>
renders as:
foo bar
So, you have to decide do you want to render the text using Nokogiri like the browser for readability, or do it accurately?
This does it like the browser:
require 'nokogiri'
doc = Nokogiri::HTML(<<EOT)
<p>Hello</p>
<p>this is <br></p>
<p>a <br></p>
<p>test message</p><br>
EOT
doc.search('br').remove
text = doc.search('p').map { |p| p.text + "\n\n" }
puts text
# >> Hello
# >>
# >> this is
# >>
# >> a
# >>
# >> test message
# >>
It removes the breaks, then converts the <p> contained text by appending two new-lines.
Doing it accurately, as per how the markup shows, is a little different:
doc.search('br').map { |br| br.replace("\n") }
text = doc.search('p').map { |p| p.text + "\n\n" }
puts text
# >> Hello
# >>
# >> this is
# >>
# >>
# >> a
# >>
# >>
# >> test message
# >>
This is just a simplified way of doing it to get you started. Rails does the opposite of this in ActionView's simple_format method.
Browsers have a lot more rules used to determine when and how to display the text and their rendering can be influenced by CSS and JavaScript which won't necessarily translate to text, especially plain text.