如果用户通过Facebook登录,而desn没有提供他的电子邮件,我如何显示错误

在我的web应用程序中,我有一个用于注册的Desive gem和2个omniauth gem(谷歌和Facebook)。情况如下:如果用户没有提供注册Facebook的电子邮件,应用程序会引发异常: Validation failed: Email can't be blank . 这就是我 from_omniauth 方法在用户模型中类似:

def self.from_omniauth(auth, sign_in_resource = nil)

    # Get the identity and usesr if they exist
    identity = Identity.find_from_oauth(auth)

    # If a signed_in_resosurce is provided it always overrides the existing user
    # to prvent the identity being locked with accidentally created accounts.
    user = sign_in_resource ? sign_in_resource : identity.user

    # Create the user if needed
    if user.nil?

      # Get the exsiting user by email *Assuming that they provide valid_email address.
      user = User.where(email: auth.info.email ).first

      # Create the user if its a new registeration
      if user.nil?
        user = User.new email: auth.info.email, password: Devise.friendly_token[0,20]

        #Disable confirmation so we don't need to send confirmation email
        # user.skip_confirmation!

        user.save!
      end
    end

    # Associate the identity with the user if needed
    if identity.user != user
      identity.user = user
      identity.save!
    end

    # Get the basic information and create Profile, Address model
    unless user.profile.present?
      first_name = auth.info.first_name.present? ? auth.info.first_name : auth.info.name.split(' ')[0]
      last_name = auth.info.last_name.present? ? auth.info.last_name : auth.info.name.split(' ')[1]
      profile = Profile.new(user_id: user.id,
                            first_name: first_name,
                            last_name: last_name,
                            gender: auth.extra.raw_info.gender)
      profile.save(validate: false)
      address = Address.new(addressable_id: profile.id, addressable_type: 'Profile')
      address.save(validate: false)
    end
    user.reload
  end

在上引发异常 user.save! 是否可以将用户重定向到其他页面,或只是显示一条flash消息?我知道业务逻辑,例如重定向和其他东西,必须在控制器中执行。那么,也许有一种方法可以将我上面写的方法移动到控制器?谢谢你了。