Custom error messages on Rails not showing up - default “is invalid” showing instead

Question

In my model, I have a simple validation like so:

class Post
    validate :max_tag_limit, if: :tags

    private
    def max_tag_limit
        errors[:tags] << "You can only have maximum of 3 tags") if tags.count > 3
    end
end

The controller adds the error messages to flash like so:

  if !@post.save
     content = "Something went wrong - "
     @post.errors.full_messages.each { |msg| content += "#{msg} : " }
     flash[:error] = content
  end

I display my error messages using this helper function in my ApplicationHelper module:

  def flash_display
    response = ""
    flash.each do |name, msg|
      response = response + content_tag(:div, msg, :id => "flash_#{name}")
    end
    flash.discard
    response
  end

I insert the message through js like so:

// add the flash message
$('#flash').html("<%= escape_javascript raw(flash_display) %>");

But i cannot for the life of me understand why Rails refuses to show my custom error message: "You can only have maximum of 3 tags". Instead it shows the rather cold inhuman message: "Tags is invalid :".

What am i doing wrong people? Help!

EDIT: Debugging reveals some more info, which should hopefully narrow my question.

 @post.errors.full_messages 

This contains only the "is invalid" message for each of my tags. I guess this means the messages i'm adding at the model, is clearly not being picked up (or is stored in the wrong location)

Answer 1

Seems you should use errors[:base] instead of errors[:tags] :

class Post
  validate :max_tag_limit, if: :tags

  private

  def max_tag_limit
    errors[:base] << "You can only have maximum of 3 tags" if tags.count > 3
  end
end

And you should not be using the flash if you're not redirecting.