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<h4 class="subsection">8.2.1 What You Can and Cannot Do in <code>+load</code></h4>
<p><code>+load</code> is to be used only as a last resort. Because it is
executed very early, most of the Objective-C runtime machinery will
not be ready when <code>+load</code> is executed; hence <code>+load</code> works
best for executing C code that is independent on the Objective-C
runtime.
<p>The <code>+load</code> implementation in the GNU runtime guarantees you the
following things:
<ul>
<li>you can write whatever C code you like;
<li>you can allocate and send messages to objects whose class is implemented
in the same file;
<li>the <code>+load</code> implementation of all super classes of a class are
executed before the <code>+load</code> of that class is executed;
<li>the <code>+load</code> implementation of a class is executed before the
<code>+load</code> implementation of any category.
</ul>
<p>In particular, the following things, even if they can work in a
particular case, are not guaranteed:
<ul>
<li>allocation of or sending messages to arbitrary objects;
<li>allocation of or sending messages to objects whose classes have a
category implemented in the same file;
<li>sending messages to Objective-C constant strings (<code>@"this is a
constant string"</code>);
</ul>
<p>You should make no assumptions about receiving <code>+load</code> in sibling
classes when you write <code>+load</code> of a class. The order in which
sibling classes receive <code>+load</code> is not guaranteed.
<p>The order in which <code>+load</code> and <code>+initialize</code> are called could
be problematic if this matters. If you don't allocate objects inside
<code>+load</code>, it is guaranteed that <code>+load</code> is called before
<code>+initialize</code>. If you create an object inside <code>+load</code> the
<code>+initialize</code> method of object's class is invoked even if
<code>+load</code> was not invoked. Note if you explicitly call <code>+load</code>
on a class, <code>+initialize</code> will be called first. To avoid possible
problems try to implement only one of these methods.
<p>The <code>+load</code> method is also invoked when a bundle is dynamically
loaded into your running program. This happens automatically without any
intervening operation from you. When you write bundles and you need to
write <code>+load</code> you can safely create and send messages to objects whose
classes already exist in the running program. The same restrictions as
above apply to classes defined in bundle.
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