代码之家 › 专栏 › 技术社区 › Joseph Weissman

充当具有多个模型的树

acts-as-tree ruby-on-rails-plugins ruby-on-rails

2

Joseph Weissman · 技术社区 · 16 年前

class Group < ActiveRecord::Base
  acts_as_tree
  has_many :users
end

class User < ActiveRecord::Base
  acts_as_tree
  belongs_to :group
  has_many :posts
end

class Post < ActiveRecord::Base
  acts_as_tree
  belongs_to :user
end

在当前的acts_as_树下,每个节点可以单独与其他节点分层关联,前提是它们具有相同的类型。我想删除对类型标识的限制,这样SomePost.parent可以有一个用户或一个Post作为它的父项,SomeUser.parent可以有另一个用户或组作为它的父项。

有什么想法吗?

2 回复 | 直到 16 年前

1

3

Toby Hede 16 年前

我过去这样做的方式是使用树中的多态容器,映射到特定的单个模型。

class Container < ActiveRecord::Base
   acts_as_tree
   belongs_to :containable, :polymorphic => true 
end

class User
  has_one :container :as => :containable
end

2

0

Translunar 16 年前

我设法做了一点不同,但这可能不适合你的情况。我不想对现有的数据库进行重构,我也不想迁移任何代码。

我在中的ClassMethods中添加了两个函数 vendor/plugins/acts_as_tree/lib/active_record/acts/tree.rb :

    # Configuration options are:
    #
    # * <tt>foreign_key</tt> - specifies the column name to use for tracking of the tree (default: +parent_id+)
    # * <tt>order</tt> - makes it possible to sort the children according to this SQL snippet.
    # * <tt>counter_cache</tt> - keeps a count in a +children_count+ column if set to +true+ (default: +false+).
    # * <tt>leaf_class_name</tt> - leaf class subtype of base tree class
    # * <tt>node_class_name</tt> - node class subtype of base tree class
    def acts_as_tree_node(options = {})
      configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil, :node_class_name => 'Node', :leaf_class_name => 'Leaf' }
      configuration.update(options) if options.is_a?(Hash)

      belongs_to :parent, :class_name => configuration[:node_class_name], :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache]
      #has_many :children, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => :destroy

      class_eval <<-EOV
        has_many :child_nodes, :class_name => '#{configuration[:node_class_name]}', :foreign_key => "#{configuration[:foreign_key]}", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}}, :dependent => :destroy
        has_many :child_leaves, :class_name => '#{configuration[:leaf_class_name]}', :foreign_key => "#{configuration[:foreign_key]}", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}}, :dependent => :destroy

        include ActiveRecord::Acts::Tree::InstanceMethods

        def self.roots
          find(:all, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
        end

        def self.root
          find(:first, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
        end
      EOV
    end

    # Configuration options are:
    #
    # * <tt>foreign_key</tt> - specifies the column name to use for tracking of the tree (default: +parent_id+)
    # * <tt>order</tt> - makes it possible to sort the children according to this SQL snippet.
    # * <tt>counter_cache</tt> - keeps a count in a +children_count+ column if set to +true+ (default: +false+).
    # * <tt>node_class_name</tt> - the class name of the node (subclass of the tree base)
    def acts_as_tree_leaf(options = {})
      configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil, :node_class_name => 'Node' }
      configuration.update(options) if options.is_a?(Hash)

      belongs_to :parent, :class_name => configuration[:node_class_name], :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache]

      class_eval <<-EOV
        include ActiveRecord::Acts::Tree::InstanceMethods

        def self.roots
          find(:all, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
        end

        def self.root
          find(:first, :conditions => "#{configuration[:foreign_key]} IS NULL", :order => #{configuration[:order].nil? ? "nil" : %Q{"#{configuration[:order]}"}})
        end
      EOV
    end

然后,在InstanceMethods中,我只添加了一个函数:

    # Returns list of children, whether nodes or leaves.
    #
    # NOTE: Will not return both, because that would take two queries and
    # order will not be preserved.
    def children
      child_leaves.count == 0 ? child_nodes : child_leaves
    end

children 函数以获得不同的行为,例如:

def children
  child_nodes | child_leaves
end

但它仍然需要一个额外的查询,您将丢失订单、范围和其他内容。

最后,在我的Node类中,我有

acts_as_tree_node :node_class_name => 'NodeMatrix', :leaf_class_name => 'LeafMatrix'

acts_as_tree_leaf :node_class_name => 'NodeMatrix'

这两个都继承自TreeMatrix,它是纯虚拟的(实际上没有任何东西被实例化为TreeMatrix,它只是一个基类)。

同样,这是非常特定于应用程序的。但它给了您一个如何修改acts_as_树的想法。