問題 docker-compose.yml mongodb: container_name: mongodb image: mongo:3.2.0 ports: - "27017:27017" myapp: container_name: myapp build: . dockerfile: Dockerfile links: - mongodb # まずはもちろんこれが必要 main.rb（抜粋） require 'mongo_mapper' MongoMapper.connection = Mongo::Connection.new('localhos…
