[#BloombergLP-balm-Metric]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/balm.adoc[balm]::Metric
:relfileprefix: ../../
:mrdocs:

This class provides an in‐core value semantic type for recording and aggregating the values of a metric. The value of a `Metric` object is characterized by the `Collector` object it uses to collect metric‐event values. Each instance of this class establishes (at construction) an association to a `Collector` object to which the metric delegates. A `Metric` value is constant after construction (i.e., it does not support assignment or provide manipulators that modify its collector value) so that synchronization primitives are not required to protect its data members. Note that if a collector or metrics manager is not supplied at construction, and if the default metrics manager has not been instantiated, then the metric will be inactive (i.e., `isActive() == false`) and the manipulator methods of the metric object will have no effect.

== Synopsis

Declared in `<balm_metric.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class Metric;
----

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/balm/Metric/2constructor-02.adoc[`Metric`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/balm/Metric/accumulateCountTotalMinMax.adoc[`accumulateCountTotalMinMax`] 
| Increase the event count by the specified `count` and add the specified `total` to the accumulated total; if the specified `min` is less than the current minimum recorded value of the metric, set the new minimum value to be `min`; if the specified `max` is greater than the current maximum recorded value, set the new maximum value to be `max`. If, however, this metric is inactive (i.e., `isActive()` is `false`), then this method has no effect.
| xref:BloombergLP/balm/Metric/collector-00.adoc[`collector`] 
| `collector` overloads
| xref:BloombergLP/balm/Metric/increment.adoc[`increment`] 
| Increase the count and total of this metric by 1; if 1.0 is less than the current minimum recorded value of the metric, set the new minimum value to be 1.0; if 1.0 is greater than the current maximum recorded value, set the new maximum value to be 1.0. If, however, this metric is not active (i.e., `isActive()` is `false`) then this method has no effect. Note that this method is functionally equivalent to `update(1)`.
| xref:BloombergLP/balm/Metric/isActive.adoc[`isActive`] 
| Return `true` if this metric will actively record metrics, and `false` otherwise. If the returned value is `false`, the manipulator operations will have no effect. A 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()`.
| xref:BloombergLP/balm/Metric/metricId.adoc[`metricId`] 
| Return a `MetricId` object identifying this metric. If this metric was not supplied a valid collector at construction then the returned id will be invalid (i.e., `metricId().isValid() == false`).
| xref:BloombergLP/balm/Metric/update.adoc[`update`] 
| Increase the event count by 1 and add the specified `value` to the total recorded value; if `value` is less than the current minimum recorded value of the metric, set the new minimum value to be `value`; if `value` is greater than the current maximum recorded value, set the new maximum value to be `value`. If, however, this metric is inactive (i.e., `isActive()` is `false`), then this method has no effect.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/balm/Metric/lookupCollector-0a.adoc[`lookupCollector`] 
| `lookupCollector` overloads
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/balm/operator_not_eq-099.adoc[`operator!=`]
| Return `true` if the specified `lhs` and `rhs` metrics do not have the same value and `false` otherwise. Two metrics do not have the same value if they record measurements using different collector objects or if one, but not both, have a null collector (i.e., `collector()` is 0).
| xref:BloombergLP/balm/operator_eq-02.adoc[`operator==`]
| Return `true` if the specified `lhs` and `rhs` metrics have the same value and `false` otherwise. Two metrics have the same value if they record measurements using the same collector object or if they both have a null collector (i.e., `collector()` is 0).
|===


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