Rails, Why a ActiveRecord Query works in a controller but not a Helper?

I have the following line of Rails 3

In the project.rb model this works great:

permissions.find_by_project_id(1).role.name

However in a projects_helper it errors "undefined method `role' for nil:NilClass":

if Permission.find_by_project_id(project_id).role.name.nil?
.
.

Why is that?

What I really want is:

current_user.permission.find_by_project_id(project_id).role.name.nil?

But that errors: "undefined method `permission' for #"

Can you help me understand ActiveRecord allowing me to build these queries?

Thanks

added info:

p开发者_StackOverflow中文版ermission.rb

class Permission < ActiveRecord::Base
    belongs_to :user 
    belongs_to :project 
    belongs_to :role 
end

project.rb

class Project < ActiveRecord::Base

    has_many :permissions
    has_many :users, :through => :permissions

end

role.rb

class Role < ActiveRecord::Base
    has_many :permissions
end

user.rb

class User < ActiveRecord::Base

    belongs_to :instance
    has_many :books
    has_many :permissions
    has_many :projects, :through => :permissions

It looks like role is not set for the given project. You can work around it by:

current_user.permissions.find_by_project_id(project_id).role.try(:name).nil?

There must be a more elegant way to write this, so feel free to suggest improvements. The point is that you have to check first that project is not nil before you can do something with project.role.

def team_member?(project_id, current_user)
  project = current_user.permissions.find_by_project_id(project_id)

  if !project.nil? && !project.role.nil?
    # your code
  else
    # return false?
  end
end