坏味道--平行继承体系(Parallel Inheritance Hierarchies) 平行继承体系(Parallel Inheritance Hierarchies) 其实是 霰弹式修改(Shotgun Surgery) 的特殊情况. 特征 每当你为某个类添加一个子类,必须同时为另一个类相应添加一个子类.这种情况的典型特征是:某个继承体系的类名前缀或类名后缀完全相同. 问题原因 起初的继承体系很小,随着不断添加新类,继承体系越来越大,也越来越难修改. 解决方法 一般策略是:让一个继承体系的…

我们已经在code-first 约定一文中,已经知道了Code-First为每一个具体的类,创建数据表. 但是你可以自己利用继承设计领域类,面向对象的技术包含“has a”和“is a”的关系即,有什么,是什么,的关系,但是基于SQL关系的实体和数据表集合之前,只是有“has a ”的关系.数据库管理系统(SQL database management systems)不支持继承类型,所以,你怎么将面向对象的领域实体和关系型的数据库映射在一起呢??? 下面有三种方式,在Code-First中表现…

type 字段在 Rails 中默认使用来做 STI(single-table inheritance),当 type 作为普通字段来使用时,可以把SIT的列设置成别的列名(比如不存在的某个列). 文档在这里http://api.rubyonrails.org/classes/ActiveRecord/ModelSchema/ClassMethods.html#method-i-inheritance_column, 使用下面的方法就是设置 STI 使用的列名,默认是‘type',既然不想使用…

Link1: Give an example Note: I think the Storable::Write method should also be pure virtual. http://www.cprogramming.com/tutorial/virtual_inheritance.html Link2: explained from the vritual table point of view, Key point: as virual inheritance, compli…

React的组合   composition: props有个特殊属性,children,组件可以通过props.children拿到所有包含在内的子元素, 当组件内有子元素时,组件属性上的children属性不生效,当组件无子元素时,属性中的children生效 function FancyBorder(props) { return ( <div className={'FancyBorder FancyBorder-' + props.color}> {props.children} &…

No classes involved; Objects inherit from other objects. Use an empty temporary constructor function  F().  Set the prototype of  F() to be the parent object. Return a new instance of the temporary constructor. function Object(o) { function F() {} F.…

// the parent constructor function Parent(name) { this.name = name || 'Adam'; } // adding functionality to the prototype Parent.prototype.say = function () { return this.name; }; // empty child constructor function Child(name) {} inherit(Child, Paren…

In Java you could do something like: Person adam = new Person(); In JavaScript you would do: var adam = new Person(); JavaScript’s constructor invocation looks as if Person were a class, but it’s important to keep in mind that Person is still just a…

Template inheritance jade支持通过关键字block和extends来实现模板继承. 比如,在layout.jade写上如下代码 html head title My Site - #{title} block scripts script(src='/jquery.js') body block content p Nothing block foot #footer p some footer content 中间的block content代表块,content表示块…

Inheritance disadvantage Unlike method invocation, inheritance violates encapsulation. Since you don't know the super class implementation which may involve some unpredictable calling between different methods of super class. And it is difficult to m…