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<overview>

<p>This metric measures, for each file, how many other files depend on it.</p>

<p>A file depends on another file if:</p>

<ul>

<li>It calls a function in that file</li>

<li>It reads or writes a variable declared in that file</li>

<li>It uses a type declared in that file</li>

</ul>

<p>Many incoming dependencies can be good or bad, depending on the nature of the file.</p>

<p>A large number of incoming dependencies is good for:</p>

<ul>

<li>files containing logging functions</li>

<li>files containing system-wide utility functions</li>

</ul>

<p>A large number of incoming dependencies may be a problem for:</p>

<ul>

<li>files that should be internal to a particular component</li>

<li>files containing functions or classes with unstable interfaces</li>

</ul>

<p>A file with many dependencies on it is risky to change, since large parts of a system

may be affected. Such files should be well documented and have clean APIs.</p>

</overview>

<recommendation>

<p>Group widely used utility functions together. Replace calls to a component's internals

with uses of its public API (augmenting it if necessary).</p>

<p>Ensure that the public API is well-documented.</p>

</recommendation>

<references>

<li>

M. Fowler. <em>Refactoring</em>. Addison-Wesley, 1999.

</li>

<li>

<a href="https://en.wikipedia.org/wiki/Code_refactoring">Wikipedia: Code refactoring</a>

</li>

<li>

<a href="http://www.jot.fm/issues/issue_2005_01/column1/">Refactoring as Meta Programming?</a>

</li>

</references>

</qhelp>