Rails and Redis: how should I handle validation here?

I'm new to rails. I am using Redis instead of something backed w/ ActiveRecord. I need to validate the presence of location, categories, start_date, and end_date. I then need to check that start_date and end_date are valid dates, that start_date comes before end_date. And that location matches a regex [A-Za-z_]. And that categories.length > 0. Since the start_date and end_date parameters in my model's setters are Date objects, should I check for valid dates and convert them in my controller. Then have my model's setters take care of the rest of the validation?

I just don't know where to put the validations: in my model or controller?

Model:

class MyThingie
  def self.set_x(location, categories, start_date, end_date, value)
    updates = {}
    for date in (start_date .. end_date)
      # ...
    end

    $redis.mset(*updates.flatten)
  end

  def self.set_y(location, categories, default)
    updates = {}
    for category in categories
      # ...
    end

    $redis.mset(*updates.flatten)
  end

  def self.set_z(location, categories, start_date, end_date, block)
    if block
      updates = {}
      for date in (start_date .. end_date)
        # ...
      end

      $redis.mset(*updates.flatten)
    else
      deletes = []
      for date in (start_date .. end_date)
        # ...
      end

      $redis.del(*deletes)
    end
  end
end

Controller:

class MyThingieController  e
      errors = [e.message]
      respond_to do |format|
        format.json do
          json = Jsonify::Builder.new
          json.errors errors
          a = json.compile!
          render :status => 400, :json => a
        end
      end
    else
      respond_to do |format|
        format.json do
          json = Jsonify::Builder.new
          json.msg "Update successful."
          a = json.compile!
          render :json => a
        end
      end
    end
  end

Here the keys are like

mythingie:location:date = value

mythingie:location:default = default

mythin

In your model.

You can include ActiveModel::Validations directly in your model without relying on ActiveRecord for persistence.

See ActiveModel::Validations & the date_validator gem

A quick example more relevant to you;

class MyThingie

  include ActiveModel::Validations

  validates :start_date, :presence => true 
  validates :end_date,   :presence => true 

  # Check out the date_validator gem, it allows things like 
  validates_date_of :end_date, :after => :start_date

  validates_format_of :location, :with => /[A-Za-z]/

  # ... 
end

StackExchange Code Review Q#9788, answer score: 4