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I am working on a website that allows users to login. All users have 1 account, an account can have many orders. A user may be a client, worker, or manager. A client is never a worker nor a manager. a manager is also a worker. I would like to present additional sections of pages/ navigation options depending on the type of user logged in.

Currently I am using a set of boolean values to mark the user as a specific type, test for that value, and run through some if/elsif blocks to generate the page that the user sees.

class User
  include DataMapper::Resource
  # ...
  # various properties
  # ...
  property :client, Boolean
  property :worker, Boolean
  property :manager, Boolean
end

And then I am using a before filter to test for the user type and set the result as variable.

before do
  @user = session[:user]
  if @user.client?
    @ura = 'client'
  elsif @user.worker?
    @ura = 'worker'
  elseif @user.manager?
    @ura = 'manager'
  end
end

Then in my views I have @ura to play around with. It seems to me that this is already going to cause me problems for managers because @ura will have to be both worker & manager. I could use some or's in my views but I think a better solution would to have the user type set as an Enum or Flag. But I don't really understand how to use that in my process.

I would like to know what the advantages/disadvantages of each are & a basic example of how I can end up with an appropriate value in @ura.

Don Wei
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2 Answers2

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I don't remember how I solved this exact issue ( I think it was for a bicycle delivery app ), but today just noticed that it is still unanswered.

So, just shy of a decade later, even though I no longer use DataMapper regularly, he is how I would solve this now;

At the time I did not understand fully the difference between authentication & authorization with respect to a users's Role in a system.

class User
  include DataMapper::Resource
  ...
  properties
  ...
  property :role, Enum[ :client, :worker, :manager ]
end

class Employee < User
  include DataMapper::Resource
  ...
   more properties
end

This way all users can have the things they need, employees could be further split into Worker & Manager. then you can put the appropriate validations on the corresponding model. More code upfront but more maintainable & more easy to scale, just add a new role to the User Enum & a corresponding class.

If the class doesn't do anything beyond namespace/logical separation you might even be able to get away with some meta programing/reflection infer the classes from the enum & include appropriate modules at initialization.

Don Wei
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I'm not sure, but may be an Array will be better solution:

class User ....
   def getRoles
      roles = Array.new
      roles << "client" if self.client? 
      roles << "manager" if self.manager? 
      roles << "worker" if self.worker? 
      roles
   end
end

before do
  @user = session[:user]
  if(@user.getRoles.index("manager") != nil)
    ...
ceth
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  • Thats Kinda similar to what I was thinking. It seems that using something like `property :role, Enum[ :client, :worker, :manager ]` would basically give me what you described in one line. My understanding is that something can only be _one_ Enum at a time. _(ie. `user.role = :worker` would overwrite whatever the current value of :role)_ Whereas a `Flag` can hold any of the defined values as a property. I get `Enum`, but I don't understand the relationships of `Flag` _(ie. How would one set & unset particular values of `Flag`? *(can they be unset once set?)* )_ – Don Wei Oct 03 '11 at 17:26
  • Ideally, I would like to be able have something like `.client?` and have that return `true` or `false`. So that I can do something like `if @ura.client?`. _(I'm fine with figuring out the code for that on my own, I'm just trying to get a handle on the best way to represent that information.)_ – Don Wei Oct 03 '11 at 17:44