In our form, let's think about what we want to do if a user enters invalid data. For example, if a user tries to enter an idea without specifying an author, we should probably not accept that. We should also not accept an idea that doesn't contain a description.

In Ruby on Rails, we can make sure that these kinds of invalid data do not get stored in the database by using validations.

There are different kinds of validations that you can use in rails (read about them here).

For now, let's write a validation to make sure that the description and author exists for every Idea.

Validations are added inside the model file. Open idea.rb. This is the model file for idea, since it is located inside the app/models directory. This is where we can add our validation. Inside your idea.rb, let's add the following piece of code to look like this:

class Idea < ApplicationRecord
  validates :description, :author, presence: true
end

So here we are saying that we want to validate that the presence is true for :description and :author.

Let's take another look at the update method:

def update
  @idea = Idea.find(params[:id])
  if @idea.update(idea_params)
    redirect_to root_path
  else
    redirect_to edit_idea_path(params[:id])
  end
end

When a validation fails, the data is not saved into the database and will return a value of false.

If a user passes in invalid data, (in this case not filling in the author or description), then the validation we just added will cause @idea.update(idea_params) to return false, thus it will go to the else statement and redirect you to the editing page once again.

Let's edit the create method to check if the idea being created is valid or not. We'll implement the details later on in the course.

We can use the valid? method to see if the idea passes all of the validations:

def create
  @idea = Idea.create(idea_params)
  if @idea.valid?
    # Implement later
  else
    # Implement later
  end
  redirect_to root_path
end

Awesome. Congratulations on writing your first validation!