What is the way to implement "business rules" in Rails?
Let us say I have a car and want to sell it:
car = Cars.find(24)
car.sell
car.sell method will check a few things:
does current_user own the car?
check: car.user_id == current_user.id
is the car listed for sale in the sales catalog?
check: car.catalogs.ids.include? car.id
if all o.k. then car is marked as sold.
I was thinking of creating a class called Rules:
class Rules
def initialize(user,car)
@user = user
@car = car
end
def can_sell_car?
@car.user_id == @user.id && @car.catalogs.ids.include? @car.id
end
end
And using it like this:
def Car
def sell
if Rules.new(current_user,self).can_sell_car
..sell the car...
else
@error_message = "Cannot sell this car"
nil
end
end
end
As for getting the current_user, I was thinking of storing it in a global variable?
I think that whenever a controller action is called, it's always a "fresh" call right? If so then storing the current user as a global variable should not introduce any risks..(like some other user being able to access another user's details)
Any insights are appreciated!
UPDATE
So, the global variable route is out! Thanks to PeterWong for pointing out that global variables persist!
I've now thinking of using this way:
class Rules
def self.can_sell_car?(current_user, car)
......checks....
end
end
And then calling Rules.can_sell_car?(current_user,@car) from the controller action.
Any thoughts on this new way?
