Loading Text Files

We've added a page_content method to the app to read contents of a wiki page from a file:

def page_content(title)
  File.read("pages/#{title}.txt")
rescue Errno::ENOENT
  return nil
end

Here's a quick explanation of page_content's code...

Ruby has a core class named File that's used for working with files. File is a subclass of the IO class, so File inherits a class method named read. File.read lets you read the entire contents of a file into a string, using only the file name. You can read more about it here in the IO.read documentation.

If the requested file isn't found, the call to File.read may raise an Errno::ENOENT exception. Normally, this would just cause processing of the HTTP request to stop in its tracks. But if we add begin and end keywords before the call that might raise an exception (or, in this case, we can skip begin and end because the code is inside a method), and add a rescue keyword, we can "rescue" our program from being halted by the exception. You can learn more about rescuing exceptions here.