工厂方法

//创建者类声明了工厂方法，必须返回product类的对象。创建者的子类//通常提供该方法的实现。创建者也可以提供一些工厂方法的默认实现。注意，尽管名字如此，但创建者的主要职责并不是创建产品。它通常包含一些核心业务逻辑，这些逻辑依赖于工厂方法返回的product //对象。子类可以通过覆盖// factory方法并从中返回不同类型的product //来间接地改变业务逻辑。method render() is //调用工厂方法创建一个产品对象。//现在使用产品。okButton.onClick(closeDialog) okButton.render() //具体创建者重写工厂方法来更改结果产品的类型。WebDialog extends Dialog is method createButton():Button is return new WindowsButton()类WebDialog extends Dialog is method createButton():Button is return new HTMLButton() //产品接口声明了所有//具体产品必须实现的操作。 interface Button is method render() method onClick(f) // Concrete products provide various implementations of the // product interface. class WindowsButton implements Button is method render(a, b) is // Render a button in Windows style. method onClick(f) is // Bind a native OS click event. class HTMLButton implements Button is method render(a, b) is // Return an HTML representation of a button. method onClick(f) is // Bind a web browser click event. class Application is field dialog: Dialog // The application picks a creator's type depending on the // current configuration or environment settings. method initialize() is config = readApplicationConfigFile() if (config.OS == "Windows") then dialog = new WindowsDialog() else if (config.OS == "Web") then dialog = new WebDialog() else throw new Exception("Error! Unknown operating system.") // The client code works with an instance of a concrete // creator, albeit through its base interface. As long as // the client keeps working with the creator via the base // interface, you can pass it any creator's subclass. method main() is this.initialize() dialog.render()