[blackboard] distinguish primitives from nested for read activity (#255)

CHANGELOG.rst

@@ -3,7 +3,7 @@ Release Notes
 
 Forthcoming
 -----------
-* ...
+* [blackboards] distinguish primitives vs nested for refined read activity detection, `#255 <https://github.com/splintered-reality/py_trees/pull/255>`_ 
 
 1.4.x (2019-11-07)
 ------------------

py_trees/blackboard.py

@@ -694,10 +694,14 @@ def __getattr__(self, name: str):
         try:
             if local_name in super().__getattribute__("write"):
                 if Blackboard.activity_stream is not None:
+                    if utilities.is_primitive(Blackboard.storage[name]):
+                        activity_type = ActivityType.READ
+                    else:  # could be a nested class object being accessed to write an attribute
+                        activity_type = ActivityType.ACCESSED
                     Blackboard.activity_stream.push(
                         self._generate_activity_item(
                             key=name,
-                            activity_type=ActivityType.ACCESSED,
+                            activity_type=activity_type,
                             current_value=Blackboard.storage[name],
                         )
                     )

py_trees/demos/blackboard.py

@@ -126,6 +126,39 @@ def update(self):
         return py_trees.common.Status.SUCCESS
 
 
+class ParamsAndState(py_trees.behaviour.Behaviour):
+    """
+    A more esotoric use of multiple blackboards in a behaviour to represent
+    storage of parameters and state.
+    """
+    def __init__(self, name="ParamsAndState"):
+        super().__init__(name=name)
+        # namespaces can include the separator or may leave it out
+        # they can also be nested, e.g. /agent/state, /agent/parameters
+        self.parameters = self.attach_blackboard_client("Params", "parameters_")
+        self.state = self.attach_blackboard_client("State", "state_")
+        self.parameters.register_key(
+            key="default_speed",
+            access=py_trees.common.Access.WRITE
+        )
+        self.state.register_key(
+            key="current_speed",
+            access=py_trees.common.Access.WRITE
+        )
+        if not self.parameters.exists("default_speed"):
+            self.parameters.default_speed = 30.0
+
+    def initialise(self):
+        self.state.current_speed = self.parameters.default_speed
+
+    def update(self):
+        if self.state.current_speed > 40.0:
+            return py_trees.common.Status.SUCCESS
+        else:
+            self.state.current_speed += 1.0
+            return py_trees.common.Status.RUNNING
+
+
 def create_root():
     root = py_trees.composites.Sequence("Blackboard Demo")
     set_blackboard_variable = py_trees.behaviours.SetBlackboardVariable(
@@ -135,7 +168,13 @@ def create_root():
     check_blackboard_variable = py_trees.behaviours.CheckBlackboardVariableValue(
         name="Check Nested Foo", variable_name="nested.foo", expected_value="bar"
     )
-    root.add_children([set_blackboard_variable, write_blackboard_variable, check_blackboard_variable])
+    params_and_state = ParamsAndState()
+    root.add_children([
+        set_blackboard_variable,
+        write_blackboard_variable,
+        check_blackboard_variable,
+        params_and_state
+    ])
     return root
 
 ##############################################################################

py_trees/utilities.py

@@ -19,6 +19,7 @@
 import os
 import re
 import traceback
+import typing
 
 ##############################################################################
 # Python Helpers
@@ -44,6 +45,20 @@ def decorate(func):
     return decorate
 
 
+@static_variables(primitives={bool, str, int, float})
+def is_primitive(incoming: typing.Any) -> bool:
+    """
+    Check if an incoming argument is a primitive type with no esoteric
+    accessors (e.g. class attributes or container [] accessors.
+
+    Args:
+        incoming: the instance to check
+    Returns:
+        True or false, depending on the check against the reserved primitives
+    """
+    return type(incoming) in is_primitive.primitives
+
+
 def truncate(original: str, length: int) -> str:
     """
     Provide an elided version of the string for which the last three