Add way to check if init has been called (i.e. isInitialized)

[chapulina]

Feature request

Feature description

It would be convenient to have a way to check if rclcpp::init has been called, similar to ros::isInitialized.

Implementation considerations

If this has been left out due to some design decision, I suppose users can live without it, and instead try to catch specific errors resulting from not calling init. I searched a bit and couldn't find an explanation, so I imagine it may just be in the backlog?

Thanks!

[sloretz]

I was going to say rclcpp::ok(), but it looks like it returns true if rclcpp hasn't been initialized. Maybe it should return false instead?

[mikaelarguedas]

would rclcpp::ok() work for your use case? (though there may be some subtle differences as it's using a global that I think would default to returning true). We could make rclcpp::init assign a value to the global and flip the default

There is indeed a related issue in the backlog: #3

[chapulina]

Yeah if g_signal_status is initialized to something other than 0 and set to 0 later, then maybe rclcpp::ok could be enough.

[sloretz]

It seems like the discussion in the waffle meeting today leaned towards having separate APIs for tracking whether a signal has been received versus whether rclcpp is currently initialized.

[wjwwood]

Closed by #522.