Added add_event_listener and remove_event_listener

README.md

@@ -150,6 +150,82 @@ data.value = "final"
 # Callback2: test -> final
 ```
 
+#### Event listener
+I can register a listener for the `ObservableEvent.AFTER_PROPERTY_CHANGE` event.
+
+```python
+from dataclasses import dataclass
+from myutils.observable import make_observable, bind, add_event_listener, ObservableEvent
+
+@dataclass
+class Data:
+  number: int = 1
+  
+data = Data()
+make_observable(data)
+
+on_change_results = []
+on_after_change_results = []
+
+def on_change(old, new):
+  on_change_results.append((old, new))
+  return new + 1
+
+def on_after_change(attr, old, new, results):
+  on_after_change_results.append((attr, old, new, results))
+
+bind(data, 'number', on_change)
+add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "number", on_after_change)
+
+data.number = 5
+data.number = 10
+
+assert on_change_results == [(1, 5), (5, 10)]
+assert on_after_change_results == [("number", 1, 5, [6]), ("number", 5, 10, [11])]
+```
+
+I can register for all attributes change events.
+
+```python
+
+from myutils.observable import make_observable, bind, add_event_listener, ObservableEvent
+
+
+class Data:
+  number: int = 1
+  value: str = "initial"
+
+
+data = Data()
+make_observable(data)
+
+
+def on_change_1(old, new):
+  return new
+
+
+def on_change_2(old, new):
+  return str(new) + "_1"
+
+
+on_after_change_results = []
+
+
+def on_after_change(attr, old, new, results):
+  on_after_change_results.append((attr, old, new, results))
+
+
+add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "", on_after_change)
+bind(data, 'number', on_change_1)
+bind(data, 'number', on_change_2)
+bind(data, 'value', on_change_1)
+
+data.number = 5
+data.value = "new value"
+
+assert on_after_change_results == [("number", 1, 5, [5, "5_1"]), ("value", "initial", "new value", ["new value"])]
+```
+
 #### Using Helper Functions
 
 ```python
@@ -319,4 +395,5 @@ Special thanks to the Python and open-source community for their tools, inspirat
 
 * 0.1.0 : Initial release
 * 0.2.0 : Observable results can be collected using `collect_return_values`
-* 0.3.0 : Added `unbind`, `unbind_all`, `has_listeners` `get_listener_count` to Observable
+* 0.3.0 : Added `unbind`, `unbind_all`, `has_listeners` `get_listener_count` to Observable
+* 0.4.0 : Added `add_event_listener` and `remove_event_listener`

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "myutils"
-version = "0.3.0"
+version = "0.4.0"
 description = "Base useful classes."
 readme = "README.md"
 authors = [

src/myutils/observable.py

@@ -1,8 +1,15 @@
+from enum import Enum
+
+
 class NotObservableError(Exception):
   def __init__(self, obj):
     super().__init__(f'{obj} is not observable')
 
 
+class ObservableEvent(Enum):
+  AFTER_PROPERTY_CHANGE = "__*after_property_change*__"
+
+
 def make_observable(obj):
   if hasattr(obj, '_listeners'):
     return obj  # Already observable
@@ -24,6 +31,16 @@ def make_observable(obj):
         for callback in self._listeners[name]:
           res.append(callback(old_value, value))
         setattr(self, '_return_values', res)
+        
+        # Trigger AFTER_PROPERTY_CHANGE event
+        after_prop_changed_event = ObservableEvent.AFTER_PROPERTY_CHANGE.value
+        if after_prop_changed_event in self._listeners:
+          if "" in self._listeners[after_prop_changed_event]:  # Trigger for all attributes
+            for callback in self._listeners[after_prop_changed_event][""]:
+              callback(name, old_value, value, res)
+          else:
+            for callback in self._listeners[after_prop_changed_event].get(name, []):
+              callback(name, old_value, value, res)
   
   obj.__class__ = ObservableVersion
   obj._listeners = {}
@@ -48,12 +65,48 @@ def bind(obj, attr_name, callback):
   obj._listeners[attr_name].append(callback)
 
 
-"""
+def add_event_listener(event: ObservableEvent, obj, attr_name, callback):
-Implementation of unbind() function for myutils.observable module.
+  if not hasattr(obj, '_listeners'):
+    raise NotObservableError(
+      f"Object must be made observable with make_observable() before binding"
+    )
+  event_name = event.value
+  if event_name not in obj._listeners:
+    obj._listeners[event_name] = {}
+  if attr_name not in obj._listeners[event_name]:
+    obj._listeners[event_name][attr_name] = []
+  obj._listeners[event_name][attr_name].append(callback)
 
-This implementation is adapted to work with the existing make_observable()
+
-and bind() functions that use the _listeners dictionary pattern.
+def remove_event_listener(event: ObservableEvent, obj, attr_name, callback):
-"""
+  if not hasattr(obj, '_listeners'):
+    raise NotObservableError(
+      f"Object must be made observable with make_observable() before binding"
+    )
+  event_name = event.value
+  if event_name not in obj._listeners:
+    return
+  if attr_name and attr_name not in obj._listeners[event_name]:
+    return
+  
+  if not attr_name:
+    for attr in list(obj._listeners[event_name].keys()):
+      if callback:
+        obj._listeners[event_name][attr].remove(callback)
+      else:
+        del obj._listeners[event_name][attr]
+  else:
+    if callback:
+      obj._listeners[event_name][attr_name].remove(callback)
+    else:
+      del obj._listeners[event_name][attr_name]
+  
+  # cleanup: remove empty attributes
+  for attr in list(obj._listeners[event_name].keys()):
+    if len(obj._listeners[event_name][attr]) == 0:
+      del obj._listeners[event_name][attr]
+      if len(obj._listeners[event_name]) == 0:
+        del obj._listeners[event_name]
 
 
 def unbind(obj, attr_name, callback):

tests/test_observable.py

@@ -1,7 +1,7 @@
 import pytest
 
 from myutils.observable import NotObservableError, make_observable, bind, collect_return_values, unbind, unbind_all, \
-  has_listeners, get_listener_count
+  has_listeners, get_listener_count, add_event_listener, ObservableEvent, remove_event_listener
 
 
 # Test fixtures
@@ -552,6 +552,337 @@ def test_i_cannot_get_listener_count_on_non_observable_object(data):
     get_listener_count(data, "value")
 
 
+# ============================================================================
+# add_event_listener() tests
+# ============================================================================
+
+def test_i_can_add_an_event_listener(observable_data):
+  """
+  add_event_listener() should correctly add a listener for a specific event and attribute.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  add_event_listener(
+    ObservableEvent.AFTER_PROPERTY_CHANGE, observable_data, "value", callback
+  )
+  
+  # Check that the listener has been added
+  event_name = ObservableEvent.AFTER_PROPERTY_CHANGE.value
+  assert event_name in observable_data._listeners
+  assert "value" in observable_data._listeners[event_name]
+  assert callback in observable_data._listeners[event_name]["value"]
+
+
+def test_i_can_add_multiple_event_listeners_for_same_attribute(observable_data):
+  """
+  Multiple event listeners can be added to the same attribute and event.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  def callback3(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "value", callback2)
+  add_event_listener(event, observable_data, "value", callback3)
+  
+  # Check that all listeners have been added
+  event_name = event.value
+  assert len(observable_data._listeners[event_name]["value"]) == 3
+  assert callback1 in observable_data._listeners[event_name]["value"]
+  assert callback2 in observable_data._listeners[event_name]["value"]
+  assert callback3 in observable_data._listeners[event_name]["value"]
+
+
+def test_i_can_handle_duplicate_event_listeners(observable_data):
+  """
+  The same callback can be added multiple times and should appear multiple times.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  
+  add_event_listener(event, observable_data, "value", callback)
+  add_event_listener(event, observable_data, "value", callback)
+  add_event_listener(event, observable_data, "value", callback)
+  
+  # Check that the same callback appears 3 times
+  event_name = event.value
+  assert len(observable_data._listeners[event_name]["value"]) == 3
+  assert observable_data._listeners[event_name]["value"].count(callback) == 3
+
+
+def test_i_cannot_add_listener_to_non_observable_object(data):
+  """
+  Trying to add an event listener to a non-observable object should raise NotObservableError.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  with pytest.raises(NotObservableError, match="must be made observable"):
+    add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "value", callback)
+
+
+# ============================================================================
+# remove_event_listener() tests
+# ============================================================================
+
+def test_i_can_remove_an_event_listener(observable_data):
+  """
+  remove_event_listener() should correctly remove a previously added listener.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  
+  # Add the listener
+  add_event_listener(event, observable_data, "value", callback)
+  
+  event_name = event.value
+  assert callback in observable_data._listeners[event_name]["value"]
+  
+  # Remove the listener
+  remove_event_listener(event, observable_data, "value", callback)
+  
+  # Check that the listener has been removed and structure cleaned up
+  assert event_name not in observable_data._listeners
+
+
+def test_i_can_remove_last_event_listener_and_clean_up_structure(observable_data):
+  """
+  Removing the last listener should clean up the internal data structures.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  add_event_listener(event, observable_data, "value", callback)
+  
+  # Verify it was added
+  assert event_name in observable_data._listeners
+  assert "value" in observable_data._listeners[event_name]
+  
+  # Remove it
+  remove_event_listener(event, observable_data, "value", callback)
+  
+  # Verify cleanup: event should be removed from _listeners
+  assert event_name not in observable_data._listeners
+
+
+def test_i_cannot_remove_listener_from_non_observable_object(data):
+  """
+  Trying to remove an event listener from a non-observable object should raise NotObservableError.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  with pytest.raises(NotObservableError, match="must be made observable"):
+    remove_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "value", callback)
+
+
+def test_i_cannot_remove_non_existent_event_listener(observable_data):
+  """
+  Trying to remove a non-existent listener should fail silently (no exception).
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  
+  # Should not raise an exception
+  remove_event_listener(event, observable_data, "value", callback)
+
+
+def test_remove_event_listener_does_not_affect_others(observable_data):
+  """
+  Removing one listener should not affect other listeners on the same attribute.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  def callback3(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Add three listeners
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "value", callback2)
+  add_event_listener(event, observable_data, "value", callback3)
+  
+  assert len(observable_data._listeners[event_name]["value"]) == 3
+  
+  # Remove only the second one
+  remove_event_listener(event, observable_data, "value", callback2)
+  
+  # Check that only callback2 was removed
+  assert len(observable_data._listeners[event_name]["value"]) == 2
+  assert callback1 in observable_data._listeners[event_name]["value"]
+  assert callback2 not in observable_data._listeners[event_name]["value"]
+  assert callback3 in observable_data._listeners[event_name]["value"]
+
+
+# ============================================================================
+# Integration tests for add/remove event listeners
+# ============================================================================
+
+def test_i_can_add_and_remove_event_listeners_sequentially(observable_data):
+  """
+  Multiple add/remove cycles should work correctly.
+  """
+  
+  def callback(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Cycle 1: Add and remove
+  add_event_listener(event, observable_data, "value", callback)
+  assert event_name in observable_data._listeners
+  
+  remove_event_listener(event, observable_data, "value", callback)
+  assert event_name not in observable_data._listeners
+  
+  # Cycle 2: Add and remove again
+  add_event_listener(event, observable_data, "value", callback)
+  assert event_name in observable_data._listeners
+  
+  remove_event_listener(event, observable_data, "value", callback)
+  assert event_name not in observable_data._listeners
+
+
+def test_listener_removal_on_multiple_event_types(observable_data):
+  """
+  Listeners for different attributes should be independently manageable.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Add listeners to different attributes
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "number", callback2)
+  
+  assert "value" in observable_data._listeners[event_name]
+  assert "number" in observable_data._listeners[event_name]
+  
+  # Remove listener from "value"
+  remove_event_listener(event, observable_data, "value", callback1)
+  
+  # Check that "value" is removed but "number" remains
+  assert "value" not in observable_data._listeners[event_name]
+  assert "number" in observable_data._listeners[event_name]
+  assert callback2 in observable_data._listeners[event_name]["number"]
+
+
+def test_i_can_remove_all_event_listener_when_attr_name_is_none(observable_data):
+  """
+  When unbind_all() is called with attr_name=None, all listeners for all attributes
+  should be removed from the observable object.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Add listeners to different attributes
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "value", callback2)
+  add_event_listener(event, observable_data, "number", callback1)
+  add_event_listener(event, observable_data, "number", callback2)
+  
+  remove_event_listener(event, observable_data, None, callback1)
+  callbacks = observable_data._listeners[event_name]["value"] + observable_data._listeners[event_name]["number"]
+  assert callback1 not in callbacks
+
+
+def test_i_can_remove_all_event_listener_when_callback_is_none(observable_data):
+  """
+  When unbind_all() is called with attr_name=None, all listeners for all attributes
+  should be removed from the observable object.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Add listeners to different attributes
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "value", callback2)
+  add_event_listener(event, observable_data, "number", callback1)
+  add_event_listener(event, observable_data, "number", callback2)
+  
+  remove_event_listener(event, observable_data, "value", None)
+  assert "value" not in observable_data._listeners[event_name]
+
+
+def test_i_can_remove_all_event_listener_when_attr_name_callback_are_none(observable_data):
+  """
+  When unbind_all() is called with attr_name=None, all listeners for all attributes
+  should be removed from the observable object.
+  """
+  
+  def callback1(attr, old, new, results):
+    pass
+  
+  def callback2(attr, old, new, results):
+    pass
+  
+  event = ObservableEvent.AFTER_PROPERTY_CHANGE
+  event_name = event.value
+  
+  # Add listeners to different attributes
+  add_event_listener(event, observable_data, "value", callback1)
+  add_event_listener(event, observable_data, "value", callback2)
+  add_event_listener(event, observable_data, "number", callback1)
+  add_event_listener(event, observable_data, "number", callback2)
+  
+  remove_event_listener(event, observable_data, None, None)
+  assert "value" not in observable_data._listeners[event_name]
+  assert "number" not in observable_data._listeners[event_name]
+
+
 # ============================================================================
 # Integration tests
 # ============================================================================
@@ -584,24 +915,133 @@ def test_multiple_bind_unbind_cycles(observable_data):
   assert len(results) == 2
 
 
-def test_same_callback_can_be_bound_to_multiple_attributes(observable_data):
+# ============================================================================
-  """
+# After property changed event
-  The same callback can be bound to multiple attributes and unbound independently.
+# ============================================================================
-  """
+
-  results = []
+
+def test_i_can_receive_changes_in_after_property_change_event(observable_data):
+  """Default case : after_property_change event should be fired when property changes."""
+  data = Data()
+  make_observable(data)
   
-  def callback(old, new):
+  on_change_results = []
-    results.append((old, new))
+  on_after_change_results = []
   
-  bind(observable_data, "value", callback)
+  def on_change(old, new):
-  bind(observable_data, "count", callback)
+    on_change_results.append((old, new))
+    return new + 1
   
-  observable_data.value = "first"
+  def on_after_change(attr, old, new, results):
-  observable_data.count = 1
+    on_after_change_results.append((attr, old, new, results))
-  assert len(results) == 2
   
-  unbind(observable_data, "value", callback)
+  bind(data, 'number', on_change)
+  add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "number", on_after_change)
   
-  observable_data.value = "second"
+  data.number = 5
-  observable_data.count = 2
+  data.number = 10
-  assert len(results) == 3  # Only count callback triggered
+  
+  assert on_change_results == [(1, 5), (5, 10)]
+  assert on_after_change_results == [("number", 1, 5, [6]), ("number", 5, 10, [11])]
+
+
+def test_i_can_receive_changes_when_multiple_properties_are_changed(observable_data):
+  """When multiple properties are changed, after_property_change event fires when all properties change."""
+  data = Data()
+  make_observable(data)
+  
+  def on_change_1(old, new):
+    return new
+  
+  def on_change_2(old, new):
+    return new + 1
+  
+  on_after_change_results = []
+  
+  def on_after_change(attr, old, new, results):
+    on_after_change_results.append((attr, old, new, results))
+  
+  bind(data, 'number', on_change_1)
+  bind(data, 'number', on_change_2)
+  add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "number", on_after_change)
+  
+  data.number = 5
+  data.number = 10
+  
+  assert on_after_change_results == [("number", 1, 5, [5, 6]), ("number", 5, 10, [10, 11])]
+
+
+def test_i_can_receive_changes_in_after_property_change_event_when_declared_first(observable_data):
+  """after_property_change event should be fired even if defined before the bindings."""
+  data = Data()
+  make_observable(data)
+  
+  def on_change(old, new):
+    return new + 1
+  
+  on_after_change_results = []
+  
+  def on_after_change(attr, old, new, results):
+    on_after_change_results.append((attr, old, new, results))
+  
+  add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "number", on_after_change)
+  bind(data, 'number', on_change)
+  
+  data.number = 5
+  data.number = 10
+  
+  assert on_after_change_results == [("number", 1, 5, [6]), ("number", 5, 10, [11])]
+
+
+def test_i_can_receive_changes_in_after_property_change_event_for_requested_attribute(observable_data):
+  """after_property_change event should be fired even if defined before the bindings."""
+  data = Data()
+  make_observable(data)
+  
+  def on_change_1(old, new):
+    return new
+  
+  def on_change_2(old, new):
+    return str(new) + "_1"
+  
+  on_after_change_results = []
+  
+  def on_after_change(attr, old, new, results):
+    on_after_change_results.append((attr, old, new, results))
+  
+  add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "number", on_after_change)
+  bind(data, 'number', on_change_1)
+  bind(data, 'number', on_change_2)
+  bind(data, 'value', on_change_1)
+  
+  data.number = 5
+  data.value = "new value"
+  
+  assert on_after_change_results == [("number", 1, 5, [5, "5_1"])]
+
+
+def test_i_can_receive_changes_in_after_property_change_event_for_all_attributes(observable_data):
+  """after_property_change event should be fired even if defined before the bindings."""
+  data = Data()
+  make_observable(data)
+  
+  def on_change_1(old, new):
+    return new
+  
+  def on_change_2(old, new):
+    return str(new) + "_1"
+  
+  on_after_change_results = []
+  
+  def on_after_change(attr, old, new, results):
+    on_after_change_results.append((attr, old, new, results))
+  
+  add_event_listener(ObservableEvent.AFTER_PROPERTY_CHANGE, data, "", on_after_change)
+  bind(data, 'number', on_change_1)
+  bind(data, 'number', on_change_2)
+  bind(data, 'value', on_change_1)
+  
+  data.number = 5
+  data.value = "new value"
+  
+  assert on_after_change_results == [("number", 1, 5, [5, "5_1"]), ("value", "initial", "new value", ["new value"])]