Question

From one ERB view, I have this helper call:

<p><%=progress @object.progress %></p>

This is the helper method (I’ve simplified it):

def progress(value)
    s = content_tag(:span, "pre:")
    s += " <strong>#{value} %</strong>"
    return s.html_safe
end

It seems that if you merge those two types of HTML strings, the latest part is not rendered properly. You’ll see this:

pre: <strong>40 %</strong>

---

If you combine the strings like so:

def progress(value)
    s = content_tag(:span, "pre:")
    s += content_tag(:strong, " #{value} %")
    return s.html_safe
end

everything work!

Answer 1

String returned from content_tag is marked as html_safe, when you add other unsafe string it’s escaped before concat.

Here’s a nice explanation on how the SafeBuffers (the class that does the html_safe magic) work: http://yehudakatz.com/2010/02/01/safebuffers-and-rails-3-0/