如果不存在，则使用#update方法创建新记录

Question

In Admin::SettingsController , I want to create a new Survey record if one does not exists, OR updates existing Survey record. What is the best Rails way to handle the creation and lookup? My error back is No route matches [POST] "/admin/settings"

edit_admin_settings_path    GET     /admin/settings/edit(.:format)  admin/settings#edit
admin_settings_path         PATCH   /admin/settings(.:format)   admin/settings#update
                            PUT     /admin/settings(.:format)   admin/settings#update

routes

resource  :settings,            only: [:edit, :update]

controller

class Admin::SettingsController < Admin::BaseController
  before_action :load_survey

  def edit
    @survey = Survey.find_or_initialize_by(id: params[:id]) unless @survey
  end

  def update
    @survey.update_attributes!(params_for_create_or_update)
    flash[:notice] = 'Survey updated'
    redirect_to action: :edit
  end

protected

  def load_survey
    @survey = Survey.last || Survey.new
  end

  def params_for_create_or_update
    params.require(:survey).permit(
      :name,
      :link,
      :language_id
    )
  end
end

Answer 1

Take a look at find_or_create_by method:

  def update
    @survey = Survey.find_or_create_by(id: params[:id])
    @survey.update_attributes!(params_for_create_or_update)
    flash[:notice] = 'Survey updated'
    redirect_to action: :edit
  end

This will try to find a record with that particular id and create one if it doesn't exist. Then you can simply update the record as you see fit.

Edit

you can also use find_or_initialize_by which calls new to instantiate the object instead of create