m[1][/_pages/] In Guardfile

Question

I was looking over Michael Hartl's online book and came across this regex line for his Guardfile.

watch(%r{^app/controllers/(.+)_(controller)\.rb$})  do |m|
    ["spec/routing/#{m[1]}_routing_spec.rb",
     "spec/#{m[2]}s/#{m[1]}_#{m[2]}_spec.rb",
     "spec/acceptance/#{m[1]}_spec.rb",
     (m[1][/_pages/] ? "spec/requests/#{m[1]}_spec.rb" : 
                       "spec/requests/#{m[1].singularize}_pages_spec.rb")]

What does the last bit do:

(m[1][/_pages/] ? "spec/requests/#{m[1]}_spec.rb" : "spec/requests/#{m[1].singularize}_pages_spec.rb")])

I get that m[1] would be the name of the controller, but what does the [/_pages/] part accomplish?

Answer 1

You can use a regex on to get a substring out of a string. It returns the first match or nil if no matches are found.

string = "foobar"
string[/[ab]/] # => "b"
string[/ab/]   # => nil

However, Michael uses it as a simple check if the regex matches. You might have seen it written with the =~ operator:

m[1] =~ /_pages/ ? something : something_else