problem with friendly URLs routing by name instead of ID

I have a route in my code that looks like this:

map.app 'applications/:title_header', :controller => 'apps', :action => 'show'

I also changed my show method in the controller to be like this:

@app = App.find_by_title_header(params[:title_header])

If I type in applications/title things work fine. If I type in applications/1 (valid Id) it fails (as expected)

However when I'm trying to use the friendly url helpers, in this case app_path(@app) the URLs that are generated look like applications/1 . The only way I can get it to work is by putting in app_path(@app.title_header). It seems like if it "just knows" that the ID is what's being passed out of t开发者_如何转开发he app object that it should "just know" that it should by default pass the name instead now. What do I need to change?

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Easiest, lightest solution is to just use to_param:

class Application < ActiveRecord::Base

  def to_param
    title_header.parameterize
  end

end

The String instance method parameterize will ensure the string is URL appropriate. Then, in your controllers you will just have to update all finds to use find_by_title_header instead of just find.

Make sure you're title_headers will be unique!

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Sounds about right. Rails doesn't assume that the symbols it encounters in a named route are methods on an object.

The best way around this is to add a custom helper to application_helper.rb, that creates takes the syntax you want to use and passes it on to a more basic version of url for.

def my_app_path(object, args)
  if object.responds_to? :title_header
    app_path(object.title_header, args)
  else 
    raise "Cannot generate url from object, missing title_header"
  end
end

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I think you need to define a to_param method on App, for one, but check out acts_as_friendly_param, which does that for you and more: http://chrisfarms.googlecode.com/svn/rails/plugins/acts_as_friendly_param/

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Actually what I ended up doing was not touching to_param. It was getting too ugly with other pages I had that needed the to_param to be an ID, not a permalink.

I ended up just passing the @app.permalink to the URL methods instead of touching to_param, but that one is still useful to know.