From c4961fb1e600f27e37d9a8bf646e1c76afafd8b6 Mon Sep 17 00:00:00 2001
From: Scott Gasch <scott@gasch.org>
Date: Thu, 1 Sep 2022 11:42:34 -0700
Subject: Easier and more self documenting patterns for loading/saving
 Persistent state via pickle and json.

---
 cached/weather_data.py     | 50 +++++++++++++++-------------------------------
 cached/weather_forecast.py | 40 +++++++++++++++++--------------------
 2 files changed, 34 insertions(+), 56 deletions(-)

(limited to 'cached')

diff --git a/cached/weather_data.py b/cached/weather_data.py
index 91d665d..86978c8 100644
--- a/cached/weather_data.py
+++ b/cached/weather_data.py
@@ -74,7 +74,7 @@ class WeatherData:
 
 
 @persistent.persistent_autoloaded_singleton()  # type: ignore
-class CachedWeatherData(persistent.Persistent):
+class CachedWeatherData(persistent.PicklingFileBasedPersistent):
     def __init__(self, weather_data: Dict[datetime.date, WeatherData] = None):
         """C'tor.  Do not pass a dict except for testing purposes.
 
@@ -207,42 +207,24 @@ class CachedWeatherData(persistent.Persistent):
                 icon=icon,
             )
 
-    @classmethod
+    @staticmethod
     @overrides
-    def load(cls) -> Any:
+    def get_filename() -> str:
+        return config.config['weather_data_cachefile']
 
-        """Depending on whether we have fresh data persisted either uses that
-        data to instantiate the class or makes an HTTP request to fetch the
-        necessary data.
-
-        Note that because this is a subclass of Persistent this is taken
-        care of automatically.
-        """
+    @staticmethod
+    @overrides
+    def should_we_save_data(filename: str) -> bool:
+        return True
 
-        if persistent.was_file_written_within_n_seconds(
-            config.config['weather_data_cachefile'],
+    @staticmethod
+    @overrides
+    def should_we_load_data(filename: str) -> bool:
+        return persistent.was_file_written_within_n_seconds(
+            filename,
             config.config['weather_data_stalest_acceptable'].total_seconds(),
-        ):
-            import pickle
-
-            with open(config.config['weather_data_cachefile'], 'rb') as rf:
-                weather_data = pickle.load(rf)
-                return cls(weather_data)
-        return None
+        )
 
     @overrides
-    def save(self) -> bool:
-        """
-        Saves the current data to disk if required.  Again, because this is
-        a subclass of Persistent this is taken care of for you.
-        """
-
-        import pickle
-
-        with open(config.config['weather_data_cachefile'], 'wb') as wf:
-            pickle.dump(
-                self.weather_data,
-                wf,
-                pickle.HIGHEST_PROTOCOL,
-            )
-        return True
+    def get_persistent_data(self) -> Any:
+        return self.weather_data
diff --git a/cached/weather_forecast.py b/cached/weather_forecast.py
index b8a20ed..7973bbb 100644
--- a/cached/weather_forecast.py
+++ b/cached/weather_forecast.py
@@ -56,7 +56,7 @@ class WeatherForecast:
 
 
 @persistent.persistent_autoloaded_singleton()  # type: ignore
-class CachedDetailedWeatherForecast(persistent.Persistent):
+class CachedDetailedWeatherForecast(persistent.PicklingFileBasedPersistent):
     def __init__(self, forecasts=None):
         if forecasts is not None:
             self.forecasts = forecasts
@@ -119,28 +119,24 @@ class CachedDetailedWeatherForecast(persistent.Persistent):
                     description=blurb,
                 )
 
-    @classmethod
+    @staticmethod
     @overrides
-    def load(cls) -> Any:
-        if persistent.was_file_written_within_n_seconds(
-            config.config['weather_forecast_cachefile'],
-            config.config['weather_forecast_stalest_acceptable'].total_seconds(),
-        ):
-            import pickle
-
-            with open(config.config['weather_forecast_cachefile'], 'rb') as rf:
-                weather_data = pickle.load(rf)
-                return cls(weather_data)
-        return None
+    def get_filename() -> str:
+        return config.config['weather_forecast_cachefile']
 
+    @staticmethod
     @overrides
-    def save(self) -> bool:
-        import pickle
-
-        with open(config.config['weather_forecast_cachefile'], 'wb') as wf:
-            pickle.dump(
-                self.forecasts,
-                wf,
-                pickle.HIGHEST_PROTOCOL,
-            )
+    def should_we_save_data(filename: str) -> bool:
         return True
+
+    @staticmethod
+    @overrides
+    def should_we_load_data(filename: str) -> bool:
+        return persistent.was_file_written_within_n_seconds(
+            filename,
+            config.config['weather_forecast_stalest_acceptable'].total_seconds(),
+        )
+
+    @overrides
+    def get_persistent_data(self) -> Any:
+        return self.forecasts
-- 
cgit v1.3