[#BloombergLP-ball-AttributeContext_RuleEvaluationCache]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/ball.adoc[ball]::AttributeContext_RuleEvaluationCache
:relfileprefix: ../../
:mrdocs:

Implementation type that evaluates and caches whether logging rules are active.

== Synopsis

Declared in `<ball_attributecontext.h>`

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

== Description

This is an implementation type of `AttributeContext` and should not be used by clients of this package. A rule evaluation cache is a mechanism for evaluating and caching whether a rule is active. A rule is considered active if all of its attributes are satisfied by the collection of attributes held in a `AttributeContainerList` object (i.e., `Rule::evaluate` returns `true` for the `AttributeContainerList` object). The rules this cache evaluates are contained in a `RuleSet` object. `RuleSet::MaskType` is a bit mask for a rule set, where each bit is a boolean value associated with the rule at the corresponding index in a rule set. An `AttributeContext` determines, using the `isDataAvailable` method, if a particular set of rules (described using a bit mask) have already been evaluated. A context accesses the current cache of rule evaluations using the `knownActiveRules` method. Finally, a context updates the cache of rule evaluations using the `update` method. Note that the `isDataAvailable` method should be used prior to using `knownActiveRules` in order to ensure the relevant rules have been evaluated and that those evaluations are up‐to‐date.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/2constructor.adoc[`AttributeContext_RuleEvaluationCache`]         [.small]#[constructor]#
| Create an empty rule evaluation cache having a sequence number of ‐1.
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/clear.adoc[`clear`] 
| Clear any currently cached rule evaluation data, restoring this object to its default constructed state (empty).
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/isDataAvailable.adoc[`isDataAvailable`] 
| Return whether this cache has up‐to‐date evaluations for the given rules.
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/knownActiveRules.adoc[`knownActiveRules`] 
| Return a bit mask of rules known to be active after the last update.
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/print.adoc[`print`] 
| Format this object to the specified output stream.
| xref:BloombergLP/ball/AttributeContext_RuleEvaluationCache/update.adoc[`update`] 
| Update the cache of rule evaluations for the specified sequence number and rules.
|===



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