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

This class defines an in‐core value‐semantic type used to identify a metric. A `MetricId` object's value is the _address_ of a non‐modifiable `MetricDescription` object. In addition, a `MetricDescription` object provides auxiliary methods, `category`, `categoryName`, and `name`, that enable access to the properties of the held `MetricDescription`. Two `MetricId` objects have the same value if the values of their respective `MetricDescription` object _addresses_ are the same.

== Synopsis

Declared in `<balm_metricid.h>`

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

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/balm/MetricId/2constructor-0c.adoc[`MetricId`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/balm/MetricId/category.adoc[`category`] 
| Return the address of the non‐modifiable `Category` object identifying the category with which this metric id is associated. The behavior is undefined unless `isValid()` is `true`. Note that this method is logically equivalent to `description()‐>category()`.
| xref:BloombergLP/balm/MetricId/categoryName.adoc[`categoryName`] 
| Return the address of the non‐modifiable name for the category with which this metric id is associated. The behavior is undefined unless `isValid()` is `true`. Note that this method is logically equivalent to `description()‐>category()‐>name()`.
| xref:BloombergLP/balm/MetricId/description-07.adoc[`description`] 
| `description` overloads
| xref:BloombergLP/balm/MetricId/isValid.adoc[`isValid`] 
| Return `true` if this metric id object contains the address of a valid `MetricDescription` object, and false `otherwise`. Note that this method is logically equivalent to `0 != description()`.
| xref:BloombergLP/balm/MetricId/metricName.adoc[`metricName`] 
| Return the address of the non‐modifiable name of this metric id. The behavior is undefined unless `isValid()` is `true`. Note that this method is logically equivalent to `description()‐>name()`.
| xref:BloombergLP/balm/MetricId/print.adoc[`print`] 
| Print this metric id to the specified output `stream` in some single‐line human‐readable form, and return a reference to the modifiable `stream`.
| xref:BloombergLP/balm/MetricId/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<MetricId, is_trivially_copyable>`] 
| Declare that this type is trivially copyable.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/balm/operator_not_eq-0f.adoc[`operator!=`]
| Return `true` if the specified `lhs` and `rhs` metric ids do not have the same value and `false` otherwise. Two metric ids do not have same value if they refer to different `MetricDescription` object _addresses_, or exactly one address is 0.
| xref:BloombergLP/balm/operator_lt.adoc[`operator<`]
| Return `true` if the specified `lhs` metric id is less than (ordered before) the specified `rhs` metric id, and return `false` otherwise'. The `lhs` is considered less if the (unsigned) _address_ of the contained `MetricDescription` object is numerically less than the `rhs` description. Note that this function does _not_ provide any form of alphabetic ordering, and is logically equivalent to the expression `lhs.description() < rhs.description()`.
| xref:BloombergLP/balm/operator_eq-0f.adoc[`operator==`]
| Return `true` if the specified `lhs` and `rhs` metric ids have the same value and `false` otherwise. Two metric ids have the same value if they each hold the address of the same `MetricDescription` object, or both addresses are 0.
|===


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