如何使用 Rails Validations 允许和属性变量成为两个值之一？

Question

For a project, I need the categories attribute of the Post class to be either "Fiction" or "Non-Fiction." I attempted the following syntax...

class CategoryValidator < ActiveModel::Validator 
    def validate(record)
        unless (record.category == "Fiction" || "Non-Fiction")
            record.errors[:category] << "Must be valid category" 
            binding.pry
        end
    end
end

but it never hit the binding.pry line, meaning it never hit "until" block, even when I entered purposefully wrong answers. What would the proper syntax for the #validate method be?

Answer 1

Your condition to check if the category is either 'Fiction' or 'Non-Fiction' isn't right.

(record.category == "Fiction" || "Non-Fiction") is evaluated as (record.category == "Fiction") || "Non-Fiction" (record.category == "Fiction") || "Non-Fiction" since == has higher precedence than || . As a result, the expression will always return "Non-Fiction" which is truthy. That's why your code never got to the binding.pry line even when the category wasn't "valid".

def validate(record)
  unless %w(Fiction Non-Fiction).include?(record.category)
    record.errors[:category] << "Must be valid category"
  end
end

A custom validator is an overkill for this use-case. You can use inclusion to add this validation.

validates :category, inclusion: {
  in: %w(Fiction Non-Fiction),
  message: 'must be either Fiction or Non-Fiction'
}

Answer 2

I hate myself, such a simple fix and I got it

class CategoryValidator < ActiveModel::Validator 
    def validate(record)
        unless (record.category == "Fiction" || record.category == "Non-Fiction")
            record.errors[:category] << "Must be valid category" 
        end
    end
end