The afferent coupling of a package is the number of types outside this package that directly depend on types inside this package.

A high afferent coupling is an indication that the package has many responsibilities; it may thus be a good idea to consider whether these responsibilities can be separated into separate packages. The main purpose of afferent coupling, however, is to define further metrics.

The precise definition of dependence between types is discussed under Afferent Coupling of a Type.

Pre-packaged Query

Query name = "Semmle/Metrics/Packages/Coupling/Packages that have high afferent coupling"

Packages that have afferent coupling greater than 20, in descending order, as a bar chart.

from MetricPackage p, int c
where p.fromSource() and c = p.getAfferentCoupling() and c > 20
select p, c order by c desc

.QL Source of Metric

This metric is defined in MetricPackage, and its definition reads:

    int getAfferentCoupling() {
      result = count(RefType t | 
                       t.getPackage() != this
                       and
                       exists(RefType s | 
                              s.getPackage()=this 
                              and
                              depends(t,s)))
    }

References

Robert C. Martin. OO Design Quality Metrics. October 24, 1994.

Robert C. Martin. Agile Software Development, Principles, Patterns and Practices. Addison Wesley, 2002.

Andrew Glover . In Pursuit of Code Quality: Code Quality for Software Architects. April 2006.

Jack Shirazi and Kirk Pepperdine. Eye on performance: Determining the riskiness of change. July 2004.