Rails Routes based on condition

问题:

I have three roles: Instuctor, Student, Admin and each have controllers with a "home" view.

so this works fine,

get "instructor/home", :to => "instructor#home"
get "student/home", :to => "student#home"
get "admin/home", :to => "admin#home"

I want to write a vanity url like below which will route based on the role of the user_id to the correct home page.

get "/:user_id/home", :to => "instructor#home" or "student#home" or "admin#home"

How do I accomplish this?

回答1:

You can't do this with routes because the routing system does not have the information required to make this decision. All Rails knows at this point of the request is what the parameters are and does not have access to anything in the database.

What you need is a controller method that can load whatever data is required, presumably the user record, and redirects accordingly using redirect_to.

This is a fairly standard thing to do.

Update:

To perform all of this within a single controller action you will need to split up your logic according to role. An example is:

class HomeController < ApplicationController
  def home
    case
    when @user.student?
      student_home
    when @user.admin?
      admin_home
    when @user.instructor
      instructor_home
    else
      # Unknown user type? Render error or use a default.
    end
  end

protected
  def instructor_home
    # ...
    render(:template => 'instructor_home')
  end

  def student_home
    # ...
    render(:template => 'student_home')
  end

  def admin_home
    # ...
    render(:template => 'admin_home')
  end
end

回答2:

I'm providing an alternate approach as this SO question comes up near the top when searching for role based routing in Rails.

I recently needed to implement something similar but wanted to avoid having a large number of conditionals in the controller - this was compounded by the fact that each of my user roles required completely different data to be loaded and presented. I opted to move the deciding logic to the routing layer by using a Routing Constraint.

# app/constraints/role_route_constraint.rb

class RoleRouteConstraint
  def initialize(&block)
    @block = block || lambda { |user| true }
  end

  def matches?(request)
    user = current_user(request)
    user.present? && @block.call(user)
  end

  def current_user(request)
    User.find_by_id(request.session[:user_id])
  end
end

The most important part of the above code is the matches? method which will determine whether or not the route will match. The method is passed the request object which contains various information about the request being made. In my case, I'm looking up the :user_id stored in the session cookie and using that to find the user making the request.

You can then use this constraint when defining your routes.

# config/routes.rb
Rails.application.routes.draw do
  get 'home', to: 'administrators#home', constraints: RoleRouteConstraint.new { |user| user.admin? }
  get 'home', to: 'instructors#home', constraints: RoleRouteConstraint.new { |user| user.instructor? }
  get 'home', to: 'students#home', constraints: RoleRouteConstraint.new { |user| user.student? }  
end

With the above in place, an administrator making a request to /home would be routed the home action of the AdministratorsController, an instructor making a request to /home would be routed to the home action of the InstructorsController, and a student making a request to /home would be routed to the home action of the StudentsController.

More Information

If you're looking for more information, I recently wrote about this approach on my blog.