Contains classes and functions for working with Condition Messages. A Condition is a high level state of your system. It could be a super-state of multiple parts of the system, or something more complex such as a intersection of a robot and a predefined volume.
Condition Publishers subscribe to one or more topics on the network, perform some predicate check on message recieved on these topics, and then publish a Condition as a result.
This package offers a ConditionPublisherNode that works out of the box, and a ConditionPublisher class that can be used to add condition publishing abilities to existing nodes.
A Condition Publisher has one or more subscriptions to topics on the network (of any type), a predicate check, and a publisher that publishes Condition messages. On receit of a new message on any of the subscribed topics, the Condition Publisher will perform the predicate check and publish a new Condition message. When multiple topics are subscribed to, it will publish Condition.UNKNOWN untill at least one message on each topic has been received.
| Type | Description |
|---|---|
| single_topic_equality | Subscribe to a single topic, and on receit of new messages publish a condition based on an equality check with predefined data. The data to compare to is given in the form of a python Dict of key-value pairs, or as a YAML string (in the case of the CLI tool). If the data matches, then the condition will be ACTIVE. |
| multi_topic_all_of_equality | Similar to single_topic_equality but for multiple topics. The data to compare to is given in the form of a python Dict of the topics, and the expected value for messages on that topic (also as a python Dict), or as YAML string (in the case of the CLI tool). If all of the messages match then the condition will be ACTIVE. It will publish UNKNOWN untill at least one message on each topic has been received. |
| multi_topic_any_of_equality | Subscribe to multiple topics and publish the Condition as ACTIVE if any of the messages match the associated data to compare to. |
| multi_topic_ex_any_of_equality | Similar to multi_topic_any_of_equality but the Condition will only be ACTIVE if one and only one of the messages match the associated data to compare to. |
Example:
class MyNode(Node):
def __init__(self):
super().__init__('my_node')
self.__condpub = ConditionPublisher() TODOTODO
The Condition Publishers wrap up Message Equality Testers. The Message Equality Testers subscribe to one or more topics and test the incoming messages against a predicate, and then call a callback function with the result of this predicate. The Condition Publisher simply sets this callback function to publish a condition message with the apropriate value.