关系和setter方法

Question

我试图覆盖一个声明关系的setter方法，以在旧节点和新节点上执行自定义行为和一些验证。

举个例子：

class FantasticTeam 
  include Neo4j::ActiveNode
  has_one :in, :active, model_class: Whatever
  has_many :in, :not_active, model_class: Whatever
  def active=(whatever)
    # return if whatever is not include in :not_active
    # add the old value to :not_active
    # delete the relationship :not_active that belongs to whatever (the param)
    # add :active relationship to whatever
  end
end

做这种事的正确方法是什么？

Answer 1

有两种方法可以处理这一问题，都比重写setter方法更容易。

第一种是在ActiveNode模型中使用回调。

class FantasticTeam 
  include Neo4j::ActiveNode
  has_one :in, :active, before: :before_callback, model_class: Whatever
  has_many :in, :not_active, model_class: Whatever
  private
  def before_callback(other)
    return false unless self.not_active.include?(other)
    self.not_active(:w, :r).where(uuid: other.uuid).pluck(:r).each { |r| r.destroy }
    self.not_active << other unless self.active.nil?
  end
end

我个人从来没有使用过这个过程。对于任何关系逻辑，我总是使用ActiveRel模型。

class FantasticTeam 
  include Neo4j::ActiveNode
  has_one :in, :active, model_class: 'Whatever', rel_class: 'FantasticActiveWhatever'
  has_many :in, :not_active, model_class: 'Whatever'
end
class FantasticActiveWhatever
  include Neo4j::ActiveRel
  from_class FantasticTeam
  to_class Whatever
  type 'ACTIVE'
  validate      :inactive
  before_create :clear_inactive
  private
  def inactive
    self.errors.add(:inactive, 'Destination node must be declared inactive') unless from_node.not_active.include?(to_node)
  end
  def clear_inactive
    from_node.not_active(:w, :r).where(uuid: to_node.uuid).pluck(:r).each { |r| r.destroy }
  end
end

然后你会创建：

rel=FantasticActiveWhatever.new（从_node：团队，到_node：随便）如果rel.save#继续结束

ActiveRel需要一些额外的设置，但它的功能要强大得多。

无论哪种方式，这都需要封装在事务中，因为存在删除not_active关系但无法设置active的可能性。

begin
  tx = Neo4j::Transaction.new
  # the whole process
rescue StandardError
  tx.failure
  # additional failure behavior, if any
ensure
  tx.close
end

基本关系回调记录在https://github.com/neo4jrb/neo4j/wiki/Neo4j-v3-Declared-Relationships#relationship-回调。

ActiveRel在https://github.com/neo4jrb/neo4j/wiki/Neo4j%3A%3AActiveRel.

交易记录在https://github.com/neo4jrb/neo4j/wiki/Transaction.