原型

//基本原型。抽象类Shape is field X: int field Y: int field color: string //正则构造函数。构造函数Shape()是//…//原型构造函数。用现有对象的值初始化一个新对象。构造函数Shape(来源:Shape)是this() this。X =源。X。Y =源。Y。Color = source。color //克隆操作返回一个Shape子类。抽象方法clone():Shape //具体的原型。 The cloning method creates a new object // in one go by calling the constructor of the current class and // passing the current object as the constructor's argument. // Performing all the actual copying in the constructor helps to // keep the result consistent: the constructor will not return a // result until the new object is fully built; thus, no object // can have a reference to a partially-built clone. class Rectangle extends Shape is field width: int field height: int constructor Rectangle(source: Rectangle) is // A parent constructor call is needed to copy private // fields defined in the parent class. super(source) this.width = source.width this.height = source.height method clone():Shape is return new Rectangle(this) class Circle extends Shape is field radius: int constructor Circle(source: Circle) is super(source) this.radius = source.radius method clone():Shape is return new Circle(this) // Somewhere in the client code. class Application is field shapes: array of Shape constructor Application() is Circle circle = new Circle() circle.X = 10 circle.Y = 10 circle.radius = 20 shapes.add(circle) Circle anotherCircle = circle.clone() shapes.add(anotherCircle) // The `anotherCircle` variable contains an exact copy // of the `circle` object. Rectangle rectangle = new Rectangle() rectangle.width = 10 rectangle.height = 20 shapes.add(rectangle) method businessLogic() is // Prototype rocks because it lets you produce a copy of // an object without knowing anything about its type. Array shapesCopy = new Array of Shapes. // For instance, we don't know the exact elements in the // shapes array. All we know is that they are all // shapes. But thanks to polymorphism, when we call the // `clone` method on a shape the program checks its real // class and runs the appropriate clone method defined // in that class. That's why we get proper clones // instead of a set of simple Shape objects. foreach (s in shapes) do shapesCopy.add(s.clone()) // The `shapesCopy` array contains exact copies of the // `shape` array's children.