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Ruby 练习问题集类变量与类方法执行下面的程序的话便发生了错误。请将程序进行修改以能正确运行。class Robot def self.ping @@count += 1 end def count @@count end end r1 = Robot.new r1.ping r2 = Robot.new r2.ping r1.ping puts Robot.countRobot类本来的形式是像下面这样:调用实例方法ping的话类的共有计数器便增加1个。调用类方法count的话便返回现在计数器的值。在终端执行此程序的话，画面上显示3。--黒田努解答与说明的显示・隐藏解答与说明这次完全不存在让 阅读全文
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http://cn.oiax.jp/rails/for_web_designers/variables_and_objects.htmlWeb设计的Ruby on Rails第2章 变量、数组、散列表这章将对生成一个变量并嵌入模板，以及 HTML 数据生成的方法进行说明。请看下面的 Ruby 程序。@title = '新闻发布'这是实例变量定义的例子。特征是以符号(@)开头。实例变量的值，可以像下面一样嵌入到模板中。<h1><%= @title %></h1>把这个和开头的程序结合在一起，便可生成下面的 HTML 代码。<h1>新 阅读全文
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A Nested Set Implementation in Java and PostgreSQLThis tutorial intends to give the reader:Themotivationsto use the Nested Set structure.Thetheorybehind the Nested Set structure.A possibleschemato implement the Nested Set.A set ofjava classesto allow the Nested Set to be used.Seean alternate impleme 阅读全文
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This acts provides Nested Set functionality. Nested Set is similiar to Tree, but with the added feature that you can select the children and all of their descendents with a single query. A good use case for this is a threaded post system, where you want to display every reply to a comment without mu 阅读全文