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<concept id="GUID-7830BAAB-40DD-5E55-84B5-8DCA888E68E7" xml:lang="en"><title>Using

TDesC</title><shortdesc>Use TDesC for interfaces which take narrow or wide (Unicode) text,

depending on the build variant, but does not change the data.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-235E272D-6F5A-5740-8150-9698C8C8D55D"><title>Usage in a

function interface</title> <p>An interface which needs access to either narrow

text or wide (Unicode) text, depending on the build variant, but which does

not need to change that data in any way, can use a <xref href="GUID-52D07F46-2162-380C-A775-C3BB335C42F5.dita"><apiname>TDesC</apiname></xref> as

the argument type. All build independent concrete descriptors are derived

from <codeph>TDesC</codeph> which means that the interface can accept any

build independent descriptor.</p> <p>The following code fragment shows the

most common function prototype pattern.</p> <codeblock id="GUID-1FAB92F0-D8D1-51C9-B993-9F0FF93659B3" xml:space="preserve">void ClassX::foo(const TDesC&amp; anArg);</codeblock> <p>The use of <codeph>TDesC</codeph> ensures that the data cannot be modified

through the descriptor; <codeph>const</codeph> is an extra guarantee that

the data cannot be changed.</p> <p>If the interface is to handle explicit

8 bit or explicit 16 bit data, regardless of the build variant, then use <codeph>TDesC8</codeph> or <codeph>TDesC16</codeph> instead.</p> </section>