CODEWITHSUNDEEP
ruby-on-rails-4
Techmago
Techmago

Reputation: 380

Rails: Get all objects with some condition

i have a class Equipment, which has a method do decide if the object is available or not. This method has some logic to check thought a has_many association, and returns true or false, so, it only work in instantiated object.

There is some way to do something like:

@someVar = Equipament.all.available

I solve this making:

equipament.rb

has_many :rents
  def available
    if(self.rents.blank?)
      return true
    else
      if(self.rents.last.end.blank?)
        return false
      else
        return true
      end
    end
  end

  def self.usable
    ary = Array.new
    Equipament.all.each do |eq|
      if eq.available
        ary.push(eq)
      end
    end
    return ary
  end

And then

@someVar = Equipament.usable

But, is this a nice way or there are something more efficient/elegant?

Upvotes: 2

Views: 1655

Answers (2)

Deepak Mahakale
Deepak Mahakale

Reputation: 23671

This should do the trick

equipament.rb

has_many :rents
def available
  (self.rents.blank? && !self.rents.last.end.blank?) ? true : false
end

def self.usable
  ary = Array.new
  Equipament.all.each do |eq|
    if eq.available
      ary.push(eq)
    end
  end
  return ary
end

Upvotes: 0

Ayman
Ayman

Reputation: 306

Apart from the infinite database queries your code could be making, the whole approach is not flexible. There could be many other reasons why the Equipment wouldn't be available other than rents. It could be in maintenance for example. That would mean making the available method even more complicated. Therefore, I believe defining a state for the Equipment would be much easier to maintain. You would change the Equipment.state based on certain events. In your case, you can change the Equipment.state to rented whenever someone rent it, and change it back to available whenever it gets returned. Not only you could now cover many more cases, but you will be also able to get a list of all available equipment with a simple method which fires only one query to the database:

# models/equipament.rb

def self.available
  where(state: :available)
end

Upvotes: 1

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