What exactly does map.connect mean?


#1

This is a beginner’s question. I am going through Agile Web
Development with Rails, First Edition. I am in chapter 16 titled
“Action Controllers and Rails” section 16.3 titled “Routing Requests”
on page 291. I have run into a conceptual mental block. I don’t
understand what EXACTLY is the function of map.connect method in the
following code:

ActionController::Routing::Routes.draw do |map|
map.connect ‘:controller/:action/:id’
end

I have just spent a couple of hours googling to look-up the references,
but everyone of those assume that you KNOW what “map.connect” means.
If someone can also point out how to go about looking up this
information in Rails API or any other suitable source, I will really
appreciate it. In other words, help me learn how to fish…

Thanks in advance.

Bharat


#2

Hi –

On Sat, 20 Jan 2007, Bharat wrote:

end

I have just spent a couple of hours googling to look-up the references,
but everyone of those assume that you KNOW what “map.connect” means.
If someone can also point out how to go about looking up this
information in Rails API or any other suitable source, I will really
appreciate it. In other words, help me learn how to fish…

In Chapter 17 of “Ruby for Rails” I offer some techniques for how to
fish through the source code – including the almighty grep, as well
as some less brute-force approaches :slight_smile: It’s not always easy, but
it’s usually very interesting and educational.

The code you’re seeing in routes.rb uses techniques defined in
routing.rb, in the ActionController library. The draw method yields a
Mapper object; “map” is that object. You then call the method
“connect” on the Mapper object. connect has the effect of registering
information about a given route with the routing system. In other
words, you’re specifying routing rules and handing them off to a
Mapper object, which then stores them in its own data structures which
it later consults when it needs to do routing.

David


Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
(See what readers are saying! http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)


#3

David’s answer is (obviously) correct - he wrote the book on the
subject. But if you looking for a beginners take on it (mine), try
this:

map.connect lets you tell Rails how you want to handle incoming
requests. The code “map.connect ‘:controller/:action/:id’” says I want
the first part of the URL to be the name of the controller followed by
a “/”, then the action followed by a “/”, then the id.

The “:” sort of says “store this in a variable called” (more
accurately, store this in the params hash with the following key). You
can actually put any key in there, but these are the conventions.


#4

Thanks gentlemen for your responses.

Andrew, it certainly helps to get someone’s perspective who is new to
rails as I am. I appreciate your response. I backtracked through the
book and re-read the first ten pages of this chapter and things are a
lot clearer now.

David, I have your book and have gone through it cover-to-cover
actually repeating a few chapters twice. I have gotten used to writing
snippets of test programs in “irb” as you do throughout your book.
Actually, I was able to locate the code in routes.rb file, but could
not understand it. As you are explaining above,

“the draw method yields a Mapper object; “map” is that object. …”

The Mapper object that you are mentioning here would be the class Route
right? which is defined in the the same source file “routes.rb”?

Coming back to irb. Is there any easy way of testing the URL to Params
hash transformation from irb? Or do I have to do it the hard way and
insert logging statements in the config/routes.rb file?

What I am trying to do is to test various mappings of URLs and
corresponding rails transforms into the Params hash as stated in the
Agile Web D. Book…"

Thanks again for your time.
Bharat


#5

I have been trying to follow-up on David’s reply above and googled
quite a bit on Routes.rb. I found Jamis B.'s blog related to this
topic at the URL below:

http://weblog.jamisbuck.org/2006/10/2/under-the-hood-rails-routing-dsl

This is very informative. One thing that puzzles me is that both David
and Jamis refer to Mapper object and I could not find a mapper object
in the file Routing.rb. As a matter of fact Jamis specifically
discusses the draw method in his article as below:

The RouteSet#draw method is where the DSL magic all begins. If you look
in the routing.rb code (around line 1113), it’s only three lines
long, but what a significant three lines those are!

def draw
clear!
yield Mapper.new(self)
named_routes.install
end

I don’t have that draw method in my Routing.rb file much less the
Mapper object! As a matter of fact, my Routing.rb file is only 716
lines long! I think that I Yum installed Ruby and then gem installed
Rails on my machine following rather simple instructions given for
Fedora Core 5 (my operating system). Everything has worked OK thus
far! I have followed David’s book from start to finish and have worked
through Agile Web D. First Edition sample application. If
someone can shed some light on this, I will really appreciate it. Note
that the path for the Routing.rb on my machine is as below:
/usr/lib/ruby/gems/1.8/gems/actionpack-1.12.5/lib/action_controller
Thanks.
Bharat


#6

Hello All,
I think that I can answer my own question (did require some work and
money). I have Chad F.'s excellent book titled ‘Rails Recipes’
where he gives a recipe to trap the routing by created in routes.rb.
It is a very easy yet quite effective way of testing the routs. This
is recipe number 36 on page 153 of his book and is called “Make Your
URLs Meaningful (and Pretty).”
Regards,
Bharat


#7

Hi –

On Mon, 22 Jan 2007, Bharat wrote:

discusses the draw method in his article as below:

I don’t have that draw method in my Routing.rb file much less the
Mapper object! As a matter of fact, my Routing.rb file is only 716
lines long! I think that I Yum installed Ruby and then gem installed
Rails on my machine following rather simple instructions given for
Fedora Core 5 (my operating system). Everything has worked OK thus
far! I have followed David’s book from start to finish and have worked
through Agile Web D. First Edition sample application. If
someone can shed some light on this, I will really appreciate it. Note
that the path for the Routing.rb on my machine is as below:
/usr/lib/ruby/gems/1.8/gems/actionpack-1.12.5/lib/action_controller

That’s an older version than the one Jamis and I are describing. If
you upgrade to the latest Rails you should have ActionPack 1.13.1, and
routing.rb in that version will have what you’re looking for.

David


Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
(See what readers are saying! http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)