has_many关系之间的查询

Question

我有一个项目模型，其中包含以下内容

has_many :project_topics
has_many :topics, :through => :project_topics

我需要一种方法来查询topic id并让它返回所有具有该主题的项目。有什么想法吗？

def projects_by_topic(topic)
end

Answer 1

我会尝试这样的事情。并查看Rails guild on ActiveRecord。

def projects_by_topic(topic)
  project_topics = ProjectTopics.where(topic_id: topic.id)
  project_topics_ids = project_topics.map {|pt| pt.id }
  projects = Project.where(project_topic_id: project_topics_ids)
end