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Lack of cohesion of methods metric

Project description

===========================
Lack of cohesion of methods
===========================

Cohesion metrics measure how well methods of a class are related to each other.
A cohesive class has one responsibility. A non-cohesive class has more
unrelated functions, thus more than one responsibility.

**LCOM4** considers method as related with other method, when both of them use common attribute or method call.
Methods are not compared with constructors / initializers eg. ``__init__``, since they often involve all attributes.
Also all inherited methods are ignored - as they come from different class.

Score:

- ``==1`` - indicates a cohesive class, which is the "good" class;
- ``>=2`` - indicates a problem. The class should be split into so many smaller classes;
- ``==0`` - happens when there are no methods in a class. This is also a "bad" class.

Usage
=====

Just point it to a module or a package that needs to be measured:

.. code-block:: cli

bin/lcom src

This will result in such output:

.. code-block:: cli

Calculating LCOM using LCOM4
+---------------------------------+------+
| Method | LCOM |
+---------------------------------+------+
| src.command.FileSystem | 1 |
| src.command.LCOMFactory | 0 |
| src.command.Printer | 0 |
| src.command.PrinterFactory | 0 |
| src.command.Runner | 1 |
| src.command.STDOut | 0 |
| src.lcom.LCOM4 | 1 |
| src.lcom.LCOMAlgorithm | 0 |
| src.reflection.ClassReflection | 1 |
| src.reflection.MethodReflection | 1 |
| src.reflection.ModuleReflection | 1 |
| src.reflection.Reflection | 0 |
| src.reflection.ReflectionError | 0 |
+---------------------------------+------+
| Average | 0.46 |
+---------------------------------+------+


It is also possible to measure single module:


.. code-block:: cli

bin/lcom src/command.py

Or mix them:

.. code-block:: cli

bin/lcom src/command.py tests

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