我正在尝试覆盖一个已声明关系的 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。
例如，举下一个例子：
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
做这样的事情的正确方法是什么？
有两种方法可以处理这个问题，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
我个人从不使用这个过程。我总是将 ActiveRel 模型用于任何关系逻辑。
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(from_node: team, to_node: 不管) if rel.save # 继续前进
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，这都需要包含在事务中，因为您可能会删除not_active关系但无法设置active.
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-callbacks。
ActiveRel 记录在https://github.com/neo4jrb/neo4j/wiki/Neo4j%3A%3AActiveRel。