subsections:

The Reactor pattern

See D.C. Schmidt, Using Design Patterns to Develop Reusable Object-oriented Communication Software, CACM October '95, 38(10): 65-74

slide: The Reactor pattern
slide: The Reactor pattern -- structure
slide: The Reactor Pattern - interaction
 


  th = new centigrade();
  th = new fahrenheit();
  th.set(f);
  f = th.get();

For thermometer th, th1; float f;

slide: Abstract system -- thermometers


  class thermometer { 
   thermometer  

  
  protected thermometer( float v ) {  temp = v; }
  
  public void set(float v) { temp = v; }
  public float get() { return temp; }
  
  protected float temp;
  };
  


  class centigrade extends thermometer { 
   centigrade  

  
  public centigrade() {  super(0);  }
  public void set(float v) { temp = v + 273; }
  public float get() { return temp - 273; }
  };
  


  class fahrenheit extends thermometer { 
   fahrenheit  

  
  public fahrenheit() { super(0); }
  public void set(float v) { temp = (v - 32) * 5/9 + 273; }
  public float get() { return temp * 9/5 + 32 - 273; }
  };
  


  class displayer extends window { 
   displayer  

  
  public displayer() { ... }
  public void put(String s) { ... }
  public void put(float f) { ... }
  };
  


  class prompter extends window { 
   prompter  

  
  public prompter(String text) { ... }
  public float get() { ... }
  public String gets() { ... }
  };
  


  abstract class event { 
   event  

  pubic void dependent(event e) { ... }
  pubic void process() { ... }
  public void operator(); // abstract method
  
  private event[] dep;
  };
  


  class update extends event { 
   update  

  
  public update(thermometer th, prompter p) {
  	_th =th;  _p = p; 
  	}
  void operator()() {
  	_th.set( _p.get() );
  	process();
  	}
  
  thermometer _th;
  prompter _p;
  };
  


  class show extends event { 
   show  

  
  public show(thermometer th, displayer d) {
  	_th = th;  _d = d; 
  	}
  public void operator() {
  	_d.put( _th.get() );
  	process();
  	}
  
  thermometer _th;
  displayer _d;
  };
  


  thermometer c = new centigrade();
  thermometer f = new fahrenheit();
  
  displayer cd = new displayer("centigrade");
  displayer fd = new displayer("fahrenheit");
  
  prompter cp = new prompter("enter centigrade value");
  prompter fp = new prompter("enter fahrenheit value");
  
  show sc = new show(c,cd);
  show sf = new show(f,fd);
  
  update uc = new update(c,cp);
  update uf = new update(f,fp);
  


  uc.dependent(sc);
  uc.dependent(sf);
  uf.dependent(sc);
  uf.dependent(sf);
  


  menu.insert(uc);
  menu.insert(uf);