I posted the following here—but thought I’d solicit other feedback via blog as well.
As of this writing, the rfacebook plugin does not seem to provide a way to handle uninstalls (easily).
Is there a method I’m not aware of? Or does one handle it pretty much how I’ve done below?
In this example, to handle uninstalls in your rails app we will use the post-remove URL of ‘foo.yourapp.com/uninstalled’.
In your application.rb, you probably have something like:
before_filter :require_facebook_install before_filter :require_facebook_login
Change your application.rb to something like:
before_filter :require_facebook_install, :except => [:uninstalled]
before_filter :require_facebook_login, :except => [:uninstalled]
# Before Filter on *only* the 'uninstalled' method
before_filter :verify_uninstall_signature, :only => [:uninstalled]
# Note: it's important this method is *above* the 'protected' definition, since it needs to be called directly
def uninstalled
@fb_uid = params[:fb_sig_user]
# From here on it will be app specific -- given the facebook uid, destroy the user, like...
@user = User.find_by_fb_uid(@fb_uid)
@user.destroy if @user
render :nothing => true; return
end
protected
...
Next, in your ‘protected’ section, add the following method which roughly corresponds to the PHP / pseudocode:
def verify_uninstall_signature
signature = ''
keys = params.keys.sort
keys.each do |key|
next if key == 'fb_sig'
next unless key.include?('fb_sig')
key_name = key.gsub('fb_sig_', '')
signature += key_name
signature += '='
signature += params[key]
end
signature += FACEBOOK['secret']
calculated_sig = Digest::MD5.hexdigest(signature)
#logger.info "\nUNINSTALL :: Signature (fb_sig param from facebook) :: #{params[:fb_sig]}"
#logger.info "\nUNINSTALL :: Signature String (pre-hash) :: #{signature}"
#logger.info "\nUNINSTALL :: MD5 Hashed Sig :: #{calculated_sig}"
if calculated_sig != params[:fb_sig]
#logger.warn "\n\nUNINSTALL :: WARNING :: expected signatures did not match\n\n"
return false
else
#logger.warn "\n\nUNINSTALL :: SUCCESS!! Signatures matched.\n"
end
return true
end
This might be handy to add to ‘rfacebook’, but it sounds like the state of that project is in flux.
Also, you might have to add this entry to your config/routes.rb file:
map.connect 'uninstalled', :controller => 'application', :action => 'uninstalled'
Happy uninstalling! :)
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