what does "use" statement do ?

rubyonrails-talk
1

I have left my ruby books at home. I am looking at some code that has stuff like

use Rack::Flash

and some other more complex statements similar to that. I am not sure what "use" does and it is too common a word to google. Any links or explanations would be appreciated ..

Thanks

2

I have left my ruby books at home. I am looking at some code that has stuff like

use Rack::Flash

This (in a rack configuration file) tells rack to add the Rack::Flash middleware to the middleware stack. Hopefully that gives you something more explicit to google for

Fred.

3

Here is another one I don't quite understand. It seems like RequestLog is used for logging http requests, but I am not sure how it is getting set up. The second part where :logger is seen doesn't quite make sense either.

Is the ruby use statement similar to the Perl use statement ? I saw some site trying to explain it in Perl a bit. I guess I need to try to locate my Programming in Ruby book tonight hopefully.

if $config['mongo']

      begin

        require 'request_log'         # customize the middleware with our own fields         use RequestLog::Middleware,                  :logger => lambda { |data| RequestLog::Db.requests.insert(data.attributes.merge({:port => data.env['SERVER_PORT'], :appname => "myapp"})) }

      end

4

RequestLog is apparently from here: http://rubydoc.info/gems/request_log/0.1.2/frames

It's starting to make a little more sense, as RequestLog::Middleware is a class I just realized, but I am not used to this type of approach ..

module RequestLog   class Middleware     def initialize(app, options = {})       @app = app       @logger = options[:logger] || lambda { | data> ::RequestLog::Db.requests.insert(data.attributes) }       @profiler = options[:profiler] || ::RequestLog::Profiler       @timeout = options[:timeout] || 0.3       @only_path = options[:only_path]     end

.. end .. end

5

Here is another one I don't quite understand. It seems like RequestLog is used for logging http requests, but I am not sure how it is getting set up. The second part where :logger is seen doesn't quite make sense either.

Is the ruby use statement similar to the Perl use statement ? I saw some site trying to explain it in Perl a bit. I guess I need to try to locate my Programming in Ruby book tonight hopefully.

There is no ruby use statement. Rack defines a use method (probably using instance_eval, which is why it looks like you're calling a top level method) that takes a class as its argument, instantiates it and pushes it onto its list of middlewares

Fred