Efferent coupling is a
coupling
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end mov ...
metric
Metric or metrical may refer to:
* Metric system, an internationally adopted decimal system of measurement
* An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement
Mathematics
In mathem ...
in
software development. It measures the number of
data types a
class knows about.
This includes
inheritance
Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Officia ...
, interface implementation, parameter types, variable types, and
exceptions.
This has also been referred to by
Robert C. Martin
Robert Cecil Martin (born 5 December 1952), colloquially called "Uncle Bob", is an American software engineer, instructor, and best-selling author. He is most recognized for developing many software design principles and for being a founder of t ...
as the Fan-out stability metric which in his book Clean Architecture he describes as Outgoing dependencies. This metric identifies the number of classes inside this component that depend on classes outside the component.
This metric is often used to calculate instability of a component in
software architecture
Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations.
...
as ''I'' = Fan-out / (Fan-in + Fan-out). This metric has a range
,1 ''I'' = 0 is maximally stable while ''I'' = 1 is maximally unstable.
References
Software metrics
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