Design patterns
ओपन प्रिंसिपल

परिचय

टिप्पणियों

खुला सिद्धांत उल्लंघन

/* 
* This design have some major issues
* For each new shape added the unit testing
* of the GraphicEditor should be redone                      
* When a new type of shape is added the time
* for adding it will be high since the developer
* who add it should understand the logic
* of the GraphicEditor.
* Adding a new shape might affect the existing
* functionality in an undesired way, 
* even if the new shape works perfectly   
*/ 

class GraphicEditor {
    public void drawShape(Shape s) {
        if (s.m_type==1)
            drawRectangle(s);
        else if (s.m_type==2)
            drawCircle(s);
    }
    public void drawCircle(Circle r) {....}
    public void drawRectangle(Rectangle r) {....}
}

 class Shape {
     int m_type;
 }

 class Rectangle extends Shape {
     Rectangle() {
         super.m_type=1;
     }
 }

 class Circle extends Shape {
     Circle() {
         super.m_type=2;
     }
 }

ओपन क्लोज प्रिंसिपल सपोर्ट

/*
* For each new shape added the unit testing
* of the GraphicEditor should not be redone
* No need to understand the sourcecode
* from GraphicEditor.
* Since the drawing code is moved to the
* concrete shape classes, it's a reduced risk
* to affect old functionallity when new
* functionallity is added.
*/ 
class GraphicEditor {
     public void drawShape(Shape s) {
         s.draw();
     }
 }

 class Shape {
     abstract void draw();
 }

 class Rectangle extends Shape  {
     public void draw() {
         // draw the rectangle
     }
 }