Return true if this integer metric will actively record metrics, and false otherwise. If the returned value is false, the manipulator operations will have no effect. An integer metric will be inactive if either (1) it was not initialized with a valid metric identifier or (2) the associated metric category has been disabled (see the MetricsManager method setCategoryEnabled). Note that invoking this method is logically equivalent to the expression 0 != collector() && metricId().category()‐>enabled().