Problems rendering a layout in Rails3

From time to time we like to share technical tips when we’ve uncovered a solution to a problem that might help other Rails developers.

Spiffy Stores is written using the Ruby on Rails framework, and we encountered a glitch with the Rails3 layouts. Basically we couldn’t get the layout to display, even though all the syntax was correct. Others have experienced this sort of problem. See http://stackoverflow.com/questions/6605716/cant-render-layout-in-rails-3 for an example.

After lots of digging around and tracing, the answer became clear. The AbstractController::Layouts module has an initialize method, but this method was not being called when a new controller was created.

If you experience this problem, then check any modules that you have included in your controller, as one of them has an initialize method that doesn’t call ‘super’.

If an included module needs an initialize method, then it needs to follow this pattern:

[ruby]
def initialize(*)
# Module initialization code here
super
end
[/ruby]

If the call to ‘super’ isn’t included, then the initialization chain stops, and your controller won’t be properly initialized. You can find out all the included modules for a controller by executing this code from the console:

[ruby]
MyController.ancestors
[/ruby]

How to Fake an Uploaded File

Our store software contains an extensive set of routines for processing uploaded images and resizing them into various image sizes. We’ve recently been adding some code to support a bulk import function and it’s become necessary to somehow fake uploading a file, given a specific URL for an image.

The basic plan is to use Net::HTTP to connect to the remote server and grab the image and save it in a temporary file. It turns out that Rails contains a UploadedTempfile class which is a subclass of Tempfile, and this is used by the CGI routines to handle any uploaded files.

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