<p>By default, the current subscriber is an empty implementation that does
nothing. To use a subscriber implementation, it must be set as the default.
There are two methods for doing so: <ahref="fn.with_default.html"title="fn tracing_core::dispatcher::with_default"><code>with_default</code></a> and
<ahref="fn.set_global_default.html"title="fn tracing_core::dispatcher::set_global_default"><code>set_global_default</code></a>. <code>with_default</code> sets the default subscriber for the
duration of a scope, while <code>set_global_default</code> sets a default subscriber
for the entire process.</p>
<p>To use either of these functions, we must first wrap our subscriber in a
<ahref="../struct.Dispatch.html"title="struct tracing_core::Dispatch"><code>Dispatch</code></a>, a cloneable, type-erased reference to a subscriber. For
<p>Then, we can use <ahref="fn.with_default.html"title="fn tracing_core::dispatcher::with_default"><code>with_default</code></a> to set our <code>Dispatch</code> as the default for
the duration of a block:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="comment">// no default subscriber
<spanclass="comment">// my_subscriber is the default
</span>});
<spanclass="comment">// no default subscriber again</span></code></pre></div>
<p>It’s important to note that <code>with_default</code> will not propagate the current
thread’s default subscriber to any threads spawned within the <code>with_default</code>
block. To propagate the default subscriber to new threads, either use
<code>with_default</code> from the new thread, or use <code>set_global_default</code>.</p>
<p>As an alternative to <code>with_default</code>, we can use <ahref="fn.set_global_default.html"title="fn tracing_core::dispatcher::set_global_default"><code>set_global_default</code></a> to
set a <code>Dispatch</code> as the default for all threads, for the lifetime of the
program. For example:</p>
<divclass="example-wrap"><preclass="rust rust-example-rendered"><code><spanclass="comment">// no default subscriber
<p>A thread’s current default subscriber can be accessed using the
<ahref="fn.get_default.html"title="fn tracing_core::dispatcher::get_default"><code>get_default</code></a> function, which executes a closure with a reference to the
currently default <code>Dispatch</code>. This is used primarily by <code>tracing</code>
</div></details><h2id="structs"class="section-header">Structs<ahref="#structs"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="struct"href="struct.DefaultGuard.html"title="struct tracing_core::dispatcher::DefaultGuard">DefaultGuard</a></div><divclass="desc docblock-short">A guard that resets the current default dispatcher to the prior
default dispatcher when dropped.</div></li><li><divclass="item-name"><aclass="struct"href="struct.Dispatch.html"title="struct tracing_core::dispatcher::Dispatch">Dispatch</a></div><divclass="desc docblock-short"><code>Dispatch</code> trace data to a <ahref="../trait.Subscriber.html"title="trait tracing_core::Subscriber"><code>Subscriber</code></a>.</div></li><li><divclass="item-name"><aclass="struct"href="struct.SetGlobalDefaultError.html"title="struct tracing_core::dispatcher::SetGlobalDefaultError">SetGlobalDefaultError</a></div><divclass="desc docblock-short">Returned if setting the global dispatcher fails.</div></li><li><divclass="item-name"><aclass="struct"href="struct.WeakDispatch.html"title="struct tracing_core::dispatcher::WeakDispatch">WeakDispatch</a></div><divclass="desc docblock-short"><code>WeakDispatch</code> is a version of <ahref="../struct.Dispatch.html"title="struct tracing_core::Dispatch"><code>Dispatch</code></a> that holds a non-owning reference
to a <ahref="../trait.Subscriber.html"title="trait tracing_core::Subscriber"><code>Subscriber</code></a>.</div></li></ul><h2id="functions"class="section-header">Functions<ahref="#functions"class="anchor">§</a></h2><ulclass="item-table"><li><divclass="item-name"><aclass="fn"href="fn.get_default.html"title="fn tracing_core::dispatcher::get_default">get_default</a></div><divclass="desc docblock-short">Executes a closure with a reference to this thread’s current <ahref="../struct.Dispatch.html"title="struct tracing_core::Dispatch">dispatcher</a>.</div></li><li><divclass="item-name"><aclass="fn"href="fn.set_default.html"title="fn tracing_core::dispatcher::set_default">set_default</a></div><divclass="desc docblock-short">Sets the dispatch as the default dispatch for the duration of the lifetime
of the returned DefaultGuard</div></li><li><divclass="item-name"><aclass="fn"href="fn.set_global_default.html"title="fn tracing_core::dispatcher::set_global_default">set_global_default</a></div><divclass="desc docblock-short">Sets this dispatch as the global default for the duration of the entire program.
Will be used as a fallback if no thread-local dispatch has been set in a thread
(using <code>with_default</code>.)</div></li><li><divclass="item-name"><aclass="fn"href="fn.with_default.html"title="fn tracing_core::dispatcher::with_default">with_default</a></div><divclass="desc docblock-short">Sets this dispatch as the default for the duration of a closure.</div></li></ul></section></div></main></body></html>
