Help/Control/NotificationCenter.html

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  24 <p class="p1"><b>NotificationCenter</b></p>
  25 <p class="p2"><br></p>
  26 <p class="p3">One common OOP pattern is Model-View-Controller where one object (the controller) is a dependant of the model.<span class="Apple-converted-space">  </span>Every time the model changes it notifies all of its dependants.<span class="Apple-converted-space">  </span>In this case the model has a dictionary of dependants and iterates through those.</p>
  27 <p class="p2"><br></p>
  28 <p class="p3">Another common pattern is NotificationCenter wherein an object emits a notification and clients can register functions that will be executed when that notification happens.</p>
  29 <p class="p2"><br></p>
  30 <p class="p3">A Server emits a \newAllocators notification when it creates new node and bus allocators which it does when it quits or boots.</p>
  31 <p class="p2"><br></p>
  32 <p class="p4"><span class="s1"><span class="Apple-tab-span">    </span></span>NotificationCenter<span class="s1">.notify(</span>Server.default<span class="s1">,</span><span class="s2">\newAllocators</span><span class="s1">);</span></p>
  33 <p class="p2"><br></p>
  34 <p class="p3">You can listen for this:</p>
  35 <p class="p2"><br></p>
  36 <p class="p4"><span class="s1"><span class="Apple-tab-span">    </span></span>NotificationCenter<span class="s1">.register(</span>Server.default<span class="s1">,</span><span class="s2">\newAllocators</span><span class="s1">,</span><span class="s2">yourself</span><span class="s1">, {</span></p>
  37 <p class="p5"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>// throw away all your node variables</p>
  38 <p class="p5"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>// or stop the music</p>
  39 <p class="p5"><span class="Apple-tab-span">     </span>});</p>
  40 <p class="p6"><br></p>
  41 <p class="p3">The Buffer class register a function to clear its info cache whenever a server restarts.<span class="Apple-converted-space">  </span>The server is emiting changed messages quite often (every 0.4 secs for the status updates), and the Buffer class is only interested in boot/quit events, so this is a more lightweight system for this purpose.</p>
  42 <p class="p6"><br></p>
  43 <p class="p7"><br></p>
  44 <p class="p8"><b>*notify(object,message,args)</b></p>
  45 <p class="p8"><span class="Apple-tab-span">     </span>The object emits a message and may also pass extra args</p>
  46 <p class="p7"><span class="Apple-tab-span">     </span></p>
  47 <p class="p8"><b>*register(object,message,listener,action)</b></p>
  48 <p class="p8"><span class="Apple-tab-span">     </span>An interested client can register the action function for the object/message notification.</p>
  49 <p class="p8"><span class="Apple-tab-span">     </span>A listener may only register one action per object/message notification.</p>
  50 <p class="p7"><span class="Apple-tab-span">     </span></p>
  51 <p class="p8"><b>*unregister(object,message,listener)</b></p>
  52 <p class="p8"><span class="Apple-tab-span">     </span>Remove the registrations</p>
  53 <p class="p7"><br></p>
  54 <p class="p8"><b>*registerOneShot(object,message,listener,action)</b></p>
  55 <p class="p8"><span class="Apple-tab-span">     </span>After the notification has been emited and handled, automatically unregister.</p>
  56 <p class="p7"><span class="Apple-tab-span">     </span></p>
  57 <p class="p8"><b>*registrationExists(object,message,listener)</b></p>
  58 <p class="p8"><span class="Apple-tab-span">     </span>Simply confirms if a registration is already in place</p>
  59 <p class="p6"><br></p>
  60 <p class="p6"><span class="Apple-tab-span">     </span></p>
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