Public interface

<h2 id="design">Design</h2>

<h3>Guidance</h3>
<p>A project must provide additional documents that describe plans and procedures that can be used to evaluate the project’s compliance.
</p>
<ul><li><a href="/facts/Building_information_modeling/VFVtPmEr">architecture design</a> document.</li>
<li><a href="/facts/Coding_conventions/oKouytzY">coding standards</a> document.</li>
<li>software release plan document.</li>
<li>document with a plan for <a href="/facts/Deprecation/1aQL7rnP">deprecating</a> obsolete interfaces.</li></ul>
<p>The programmer must create fully insulated classes and insulate the  public interfaces from <a href="/facts/Compile_time/yCdI3oqn">compile-time</a> dependencies.
</p>
<h3>Best practices</h3>
<ul><li>Present complete and coherent sets of <a href="/facts/Concept/VWB6yhQp">concepts</a> to the user.</li>
<li>Design interfaces to be statically typed.</li>
<li>Minimize the interface’s dependencies on other interfaces.</li>
<li>Express interfaces in terms of application-level types.</li>
<li>Use assertions only to aid development and integration.</li></ul>
<h3>Example</h3>
<h3>C++ interface</h3>
Use protocol classes to define public interfaces.
The characteristics of a protocol class are:
<ul><li>It neither contains nor inherits from classes that contain member data, non-virtual functions, or private (or protected) members of any kind.</li>
<li>It has a non-inline virtual destructor defined with an empty implementation.</li>
<li>All member functions other than the destructor, including inherited functions, are declared pure virtual and left undefined.</li></ul>
Benefits
The benefits of using protocol classes include:
<ul><li>Insulating applications from the external client</li>
<li>Insulating changes that are internal to the interface</li>
<li>Insulating changes to the public interface from changes to the implementation of the interface</li>
<li>Insulation has costs, but these tend to be outweighed by the gains in <a href="/facts/Interoperability/7WgqUbXU">interoperability</a> and reusability.</li></ul>
Costs:
<ul><li>Going through the implementation pointer</li>
<li>Addition of one level of indirection per access</li>
<li>Addition of the size of the implementation pointer per object to memory requirements</li></ul>
<h2 id="other-information">Other information</h2>
<p>Various <a href="/facts/Methodology/dk5X9Hxx">methodologies</a>, such as <a href="/facts/Refactoring/gkw9oVTE">refactoring</a>, support the determination of interfaces. Refactoring generally applies to the entire software implementation, but is especially helpful in properly flushing out interfaces.  There are other approaches defined through the pattern community.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a>
</p>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"Design Patterns Library". hillside.net. Retrieved 2022-11-24. <a href="https://hillside.net/patterns/" target="_blank">https://hillside.net/patterns/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
</ol>

Public interface open-in-new

Public interface