of its lifetime, it may
maintain an invariant guaranteeing that the instance variable is always released
before -dealloc. In this case, you can silence a warning about a missing release
by either adding <tt>assert(_ivar == nil)</tt> or an explicit release
<tt>[_ivar release]</tt> (which will be a no-op when the variable is nil) in
-dealloc. </p>

<h4 id="decide_nullability" class="faq">Q: How do I decide whether a method's return type should be _Nullable or _Nonnull?</h4>

<p> Depending on the implementatio