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docs/source/Weather-Tutorial.md

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+# Weather Tutorial
+
+
+This tutorial will have us create a simple weather system for our MUD.  The way we want to use this is to have all outdoor rooms echo weather-related messages to the room at regular and semi-random intervals. Things like "Clouds gather above", "It starts to rain" and so on. 
+
+One could imagine every outdoor room in the game having a script running on themselves that fires regularly. For this particular example it is however more efficient to do it another way, namely by using a "ticker-subscription" model. The principle is simple: Instead of having each Object individually track the time, they instead subscribe to be called by a global ticker who handles time keeping.  Not only does this centralize and organize much of the code in one place, it also has less computing overhead. 
+
+Evennia offers the [TickerHandler](TickerHandler) specifically for using the subscription model. We will use it for our weather system. 
+
+We will assume you know how to make your own Typeclasses. If not see one of the beginning tutorials. We will create a new WeatherRoom typeclass that is aware of the day-night cycle.
+
+```python
+
+    import random
+    from evennia import DefaultRoom, TICKER_HANDLER
+    
+    ECHOES = ["The sky is clear.", 
+              "Clouds gather overhead.",
+              "It's starting to drizzle.",
+              "A breeze of wind is felt.",
+              "The wind is picking up"] # etc  
+
+    class WeatherRoom(DefaultRoom):
+        "This room is ticked at regular intervals"        
+       
+        def at_object_creation(self):
+            "called only when the object is first created"
+            TICKER_HANDLER.add(60 * 60, self.at_weather_update)
+
+        def at_weather_update(self, *args, **kwargs):
+            "ticked at regular intervals"
+            echo = random.choice(ECHOES)
+            self.msg_contents(echo)
+```
+
+In the `at_object_creation` method, we simply added ourselves to the TickerHandler and tell it to call `at_weather_update` every hour (`60*60` seconds). During testing you might want to play with a shorter time duration.
+
+For this to work we also create a custom hook `at_weather_update(*args, **kwargs)`, which is the call sign required by TickerHandler hooks.
+
+Henceforth the room will inform everyone inside it when the weather changes. This particular example is of course very simplistic - the weather echoes are just randomly chosen and don't care what weather came before it. Expanding it to be more realistic is a useful exercise.