Sustainable Web Development with Ruby on Rails:

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1

Title: Sustainable Web Development with Ruby on Rails: Regex incorrect (testing Helpers section)

This code fails:

“# test/helpers/application_helper_test.rb

class ApplicationHelperTest < ActionView::TestCase
test “styled_widget_id” do
rendered_component = styled_widget_id(“1.23”)
→
→ regexp = %r{
→ <span # match a span tag
→ [^>]* # ignore anything that isn’t >
→ > # match the > to close the opening tag
→ .* # anything at all in here (e.g. other tags)
→ 1.23 # the widget ID we expect, escaping the dot
→ .* # anything after it (e.g. other tags)
→ # closing span tag
→ }x

assert_match regexp, rendered_component
 assert rendered_component.html_safe?
end

end

The line:
→ [^>]* # ignore anything that isn’t >
should be:
→ .* # ignore anything that isn’t >

2

I’m surprised this fails. The book executes this code when it’s run and that regexp should be correct.

Without the %r{..}x formatting, the regular expression in the book is:

regexp = /<span[^>]*>.*1\.23.*<\/span>/

And this does match the two strings in the book:

> regexp.match?('<span style="font-family: monospace">1.23</span>')
=> true
> regexp.match?('<span class="mono">1.23</span>') 
=> true

I did notice that copying and pasting from the PDF doesn’t copy the regular expression properly. Unfortunately, the tools I use to build the book result in weird uncopyable code blocks.

Can you try copying the code straight from the .zip files and see what happens?

3

Hi david,

Well that’s embarrassing…
I copied from the book again into a small test program (versus my previous test into the code for the widgets app), and it worked!
I must have had a typo.

However I did notice and forgot to mention that in the book there is a mistake in the line:

“→ # closing span tag”

the “/“ is not escaped.

My apologies for my screw-up.

Love the book.

Cheers,
Rob

4

That slash in the book does not need to be escaped because of the use of %r{...} syntax for regexps:

> x = %r{/span}
=> /\/span/
> "</span>".match?(x)
=> true
5

Thanks for the clarification David.
My noob status is obviously showing.

Cheers,
Rob

6

Heh, don’t sweat it. Regex is pretty complicated and requires a ton of trial and error, even if you think you’ve got it figured out :slight_smile:

7

Appreciate your allowances. :grinning: