Ruby on Rails：如何在模型中创建初始化方法，还是应该在控制器中设置所有默认参数？

Question

I have a field in my model for date created, this is not passed from the form and is currently set in the create method of my controller.

Should this be in my model instead in some sort of initializer method? If so what would that method look like?

I have other fields I want to set as a default each a record is created so I'm trying to find out where is the accepted standard place to put these. I'm starting to think it should be the model as if the model was ever called outside the controller it wouldn't have all this logic.

Answer 1

I generally create builders and never use directly the standard Rails method create .

The point is to gather all the logic in one place with particular cases etc...

Basically in controllers I end up calling the builders this way:

@my_model_instance = MyModelBuilder.new(current_user, params[:my_model]).build

@my_model_instance = MyModelBuilder.new(current_user, params[:my_model]).create

All my builders live in /app/builders

---

Here is a very basic example:

class MyModelBuilder

  attr_accessor :params, :user, :my_model

  # consider using a Struct if you keep a very basic initializer
  def initialize(user, params)
    self.user = user
    self.params = params
  end

  def build
    my_model
  end

  def create
    my_model.tap{|m| m.save }
  end

  def my_model
    @my_model ||= MyModel.new(default_values.merge(params))
  end

  def default_values
    {
      foo: 'bar'
    }
  end
end

Answer 2

Rails already manages the date of creation and update of your records.

If your model has a created_at field or an updated_at field they will be filled with the time of creation and update of your model.

You can generate those fields easily in a migration, for instance :

create_table :hello do
  t.timestamps
end

Now, for default values, you can fill them in the initialize method of the model :

def initialize(*args)
  self.field = default_value
  super(*args)
end