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发表时间:2007-06-22
1,tree.rb module ActiveRecord module Acts module Tree def self.included(base) base.extend(ClassMethods) end module ClassMethods def acts_as_tree(options = {}) configuration = { :foreign_key => "parent_id", :order => nil, :counter_cache => nil } configuration.update(options) if options.is_a?(Hash) belongs_to :parent, :class_name => name, :foreign_key => configuration[:foreign_key], :counter_cache => configuration[:counter_cache] has_many :children, :class_name => name, :foreign_key => configuration[:foreign_key], :order => configuration[:order], :dependent => :destroy 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 end module InstanceMethods def ancestors node, nodes = self, [] nodes << node = node.parent while node.parent nodes end def root node = self node = node.parent while node.parent node end def siblings self_and_siblings - [self] end def self_and_siblings parent ? parent.children : self.class.roots end end end end end 从上面的代码我们学习到如下几点: 1) acts_as_tree实际上定义了belongs_to :parent和has_many :children,也就是说我们可以通过@model.parent和@model.children得到父子对象 2) acts_as_tree的配置参数有:foreign_key、:order => nil和:counter_cache 3) 其中定义了roots和root这两个Class Methods 4) 其中还定义了ancestors、root、sliblings、self_and_siblings这些Instance Methods 2,list.rb module ActiveRecord module Acts module List def self.included(base) base.extend(ClassMethods) end module ClassMethods def acts_as_list(options = {}) configuration = { :column => "position", :scope => "1 = 1" } configuration.update(options) if options.is_a?(Hash) configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ /_id$/ if configuration[:scope].is_a?(Symbol) scope_condition_method = %( def scope_condition if #{configuration[:scope].to_s}.nil? "#{configuration[:scope].to_s} IS NULL" else "#{configuration[:scope].to_s} = \#{#{configuration[:scope].to_s}}" end end ) else scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end" end class_eval <<-EOV include ActiveRecord::Acts::List::InstanceMethods def acts_as_list_class ::#{self.name} end def position_column '#{configuration[:column]}' end #{scope_condition_method} after_destroy :remove_from_list before_create :add_to_list_bottom EOV end end module InstanceMethods def insert_at(position = 1) insert_at_position(position) end def move_lower return unless lower_item acts_as_list_class.transaction do lower_item.decrement_position increment_position end end def move_higher return unless higher_item acts_as_list_class.transaction do higher_item.increment_position decrement_position end end def move_to_bottom return unless in_list? acts_as_list_class.transaction do decrement_positions_on_lower_items assume_bottom_position end end def move_to_top return unless in_list? acts_as_list_class.transaction do increment_positions_on_higher_items assume_top_position end end def remove_from_list decrement_positions_on_lower_items if in_list? end def increment_position return unless in_list? update_attribute position_column, self.send(position_column).to_i + 1 end def decrement_position return unless in_list? update_attribute position_column, self.send(position_column).to_i - 1 end def first? return false unless in_list? self.send(position_column) == 1 end def last? return false unless in_list? self.send(position_column) == bottom_position_in_list end def higher_item return nil unless in_list? acts_as_list_class.find(:first, :conditions => "#{scope_condition} AND #{position_column} = #{(send(position_column).to_i - 1).to_s}" ) end def lower_item return nil unless in_list? acts_as_list_class.find(:first, :conditions => "#{scope_condition} AND #{position_column} = #{(send(position_column).to_i + 1).to_s}" ) end def in_list? !send(position_column).nil? end private def add_to_list_top increment_positions_on_all_items end def add_to_list_bottom self[position_column] = bottom_position_in_list.to_i + 1 end def scope_condition() "1" end def bottom_position_in_list(except = nil) item = bottom_item(except) item ? item.send(position_column) : 0 end def bottom_item(except = nil) conditions = scope_condition conditions = "#{conditions} AND #{self.class.primary_key} != #{except.id}" if except acts_as_list_class.find(:first, :conditions => conditions, :order => "#{position_column} DESC") end def assume_bottom_position update_attribute(position_column, bottom_position_in_list(self).to_i + 1) end def assume_top_position update_attribute(position_column, 1) end def decrement_positions_on_higher_items(position) acts_as_list_class.update_all( "#{position_column} = (#{position_column} - 1)", "#{scope_condition} AND #{position_column} <= #{position}" ) end def decrement_positions_on_lower_items return unless in_list? acts_as_list_class.update_all( "#{position_column} = (#{position_column} - 1)", "#{scope_condition} AND #{position_column} > #{send(position_column).to_i}" ) end def increment_positions_on_higher_items return unless in_list? acts_as_list_class.update_all( "#{position_column} = (#{position_column} + 1)", "#{scope_condition} AND #{position_column} < #{send(position_column).to_i}" ) end def increment_positions_on_lower_items(position) acts_as_list_class.update_all( "#{position_column} = (#{position_column} + 1)", "#{scope_condition} AND #{position_column} >= #{position}" ) end def increment_positions_on_all_items acts_as_list_class.update_all( "#{position_column} = (#{position_column} + 1)", "#{scope_condition}" ) end def insert_at_position(position) remove_from_list increment_positions_on_lower_items(position) self.update_attribute(position_column, position) end end end end end 从上面的代码我们学习到,acts_as_list的配置参数有:column和:scope 1) :column默认名为position 2) :scope后的参数为symbol时,如果没有_id则加上_id后缀 class TodoList < ActiveRecord::Base has_many :todo_items, :order => "position" end class TodoItem < ActiveRecord::Base belongs_to :todo_list acts_as_list :scope => :todo_list end 这样生成的scope_condition为"todo_list_id = #{todo_list_id}" 3) :scope后的参数为string时可以进行细粒度的限制 class TodoList < ActiveRecord::Base has_many :todo_items, :order => "position" end class TodoItem < ActiveRecord::Base belongs_to :todo_list acts_as_list :scope => 'todo_list_id = #{todo_list_id} AND completed = 0' end 4) 实例方法很多,简单看看即可,不一一介绍了 3,nested_set.rb module ActiveRecord module Acts module NestedSet def self.included(base) base.extend(ClassMethods) end module ClassMethods def acts_as_nested_set(options = {}) configuration = { :parent_column => "parent_id", :left_column => "lft", :right_column => "rgt", :scope => "1 = 1" } configuration.update(options) if options.is_a?(Hash) configuration[:scope] = "#{configuration[:scope]}_id".intern if configuration[:scope].is_a?(Symbol) && configuration[:scope].to_s !~ /_id$/ if configuration[:scope].is_a?(Symbol) scope_condition_method = %( def scope_condition if #{configuration[:scope].to_s}.nil? "#{configuration[:scope].to_s} IS NULL" else "#{configuration[:scope].to_s} = \#{#{configuration[:scope].to_s}}" end end ) else scope_condition_method = "def scope_condition() \"#{configuration[:scope]}\" end" end class_eval <<-EOV include ActiveRecord::Acts::NestedSet::InstanceMethods #{scope_condition_method} def left_col_name() "#{configuration[:left_column]}" end def right_col_name() "#{configuration[:right_column]}" end def parent_column() "#{configuration[:parent_column]}" end EOV end end module InstanceMethods def root? parent_id = self[parent_column] (parent_id == 0 || parent_id.nil?) && (self[left_col_name] == 1) && (self[right_col_name] > self[left_col_name]) end def child? parent_id = self[parent_column] !(parent_id == 0 || parent_id.nil?) && (self[left_col_name] > 1) && (self[right_col_name] > self[left_col_name]) end def unknown? !root? && !child? end def add_child( child ) self.reload child.reload if child.root? raise "Adding sub-tree isn\'t currently supported" else if ( (self[left_col_name] == nil) || (self[right_col_name] == nil) ) self[left_col_name] = 1 self[right_col_name] = 4 return nil unless self.save child[parent_column] = self.id child[left_col_name] = 2 child[right_col_name]= 3 return child.save else child[parent_column] = self.id right_bound = self[right_col_name] child[left_col_name] = right_bound child[right_col_name] = right_bound + 1 self[right_col_name] += 2 self.class.base_class.transaction { self.class.base_class.update_all( "#{left_col_name} = (#{left_col_name} + 2)", "#{scope_condition} AND #{left_col_name} >= #{right_bound}" ) self.class.base_class.update_all( "#{right_col_name} = (#{right_col_name} + 2)", "#{scope_condition} AND #{right_col_name} >= #{right_bound}" ) self.save child.save } end end end def children_count return (self[right_col_name] - self[left_col_name] - 1)/2 end def full_set self.class.base_class.find(:all, :conditions => "#{scope_condition} AND (#{left_col_name} BETWEEN #{self[left_col_name]} and #{self[right_col_name]})" ) end def all_children self.class.base_class.find(:all, :conditions => "#{scope_condition} AND (#{left_col_name} > #{self[left_col_name]}) and (#{right_col_name} < #{self[right_col_name]})" ) end def direct_children self.class.base_class.find(:all, :conditions => "#{scope_condition} and #{parent_column} = #{self.id}") end def before_destroy return if self[right_col_name].nil? || self[left_col_name].nil? dif = self[right_col_name] - self[left_col_name] + 1 self.class.base_class.transaction { self.class.base_class.delete_all( "#{scope_condition} and #{left_col_name} > #{self[left_col_name]} and #{right_col_name} < #{self[right_col_name]}" ) self.class.base_class.update_all( "#{left_col_name} = (#{left_col_name} - #{dif})", "#{scope_condition} AND #{left_col_name} >= #{self[right_col_name]}" ) self.class.base_class.update_all( "#{right_col_name} = (#{right_col_name} - #{dif} )", "#{scope_condition} AND #{right_col_name} >= #{self[right_col_name]}" ) } end end end end end 我们可以得到如下几点: 1) acts_as_nested_set和acts_as_tree很类似,但是多一个特性是可以一条语句查询出所有的children def all_children self.class.base_class.find(:all, :conditions => "#{scope_condition} AND (#{left_col_name} > #{self[left_col_name]}) and (#{right_col_name} < #{self[right_col_name]})" ) end 以及高效率的计算children_count def children_count return (self[right_col_name] - self[left_col_name] - 1)/2 end 2) acts_as_nested_set的参数为:parent_column、:left_column、:right_column和:scope 3) 这种数据结构常用在threaded post system等场景 看了上述代码,相信大家可以自己动手写acts_as_xx数据结构了 BTW:对ActiveRecord源码的研究告一段落,还有query_cache/observer/xml_serialization/timestamp/calculations/migration等留待大家自己研究 接下来看看ActionController吧 声明:ITeye文章版权属于作者,受法律保护。没有作者书面许可不得转载。
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发表时间:2007-06-22
javaeye的表情替代符号真是让人伤心
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发表时间:2007-06-23
migration还是很有意思的
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发表时间:2007-06-24
migration的核心方法:
def migrate(direction) return unless respond_to?(direction) case direction when :up then announce "migrating" when :down then announce "reverting" end result = nil time = Benchmark.measure { result = send("real_#{direction}") } case direction when :up then announce "migrated (%.4fs)" % time.real; write when :down then announce "reverted (%.4fs)" % time.real; write end result end DHH在RailsConf2007上介绍Rails 2.0的Speech中的形容的是“Sexy Migrations”: create_table :people do |t| t.account_id :type => :integer end 或者更cool的 create_table :people do |t| t.integer :account_id end 再也不用 create_table :people do |t| t.column :account_id, :integer end |
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发表时间:2007-06-24
rails2.0什么时候发布呢?有说日期吗?
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