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<section id='main' class="content struct">
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<h1 class='fqn'><span class='in-band'>Struct <a href='../../index.html'>bitflags</a>::<wbr><a href='../index.html'>__core</a>::<wbr><a href='index.html'>sync</a>::<wbr><a class='struct' href=''>Weak</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a id='src-367' class='srclink' href='https://doc.rust-lang.org/nightly/alloc/arc/struct.Weak.html?gotosrc=367' title='goto source code'>[src]</a></span></h1>
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<pre class='rust struct'>pub struct Weak<T> <span class='where'>where T: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span> {
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// some fields omitted
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}</pre><span class="since">1.4.0</span><div class='docblock'><p>A weak pointer to an <code>Arc</code>.</p>
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<p>Weak pointers will not keep the data inside of the <code>Arc</code> alive, and can be
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used to break cycles between <code>Arc</code> pointers.</p>
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</div><h2 id='methods'>Methods</h2><h3 class='impl'><code>impl<T> <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T></code></h3><div class='impl-items'><h4 id='method.new' class='method'><code>fn <a href='#method.new' class='fnname'>new</a>() -> <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T></code></h4>
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<div class='stability'><em class='stab unstable'>Unstable (<code>downgraded_weak</code>)<p>: recently added</p>
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</em></div><div class='docblock'><p>Constructs a new <code>Weak<T></code> without an accompanying instance of T.</p>
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<p>This allocates memory for T, but does not initialize it. Calling
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Weak<T>::upgrade() on the return value always gives None.</p>
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<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='attribute'>#<span class='op'>!</span>[<span class='ident'>feature</span>(<span class='ident'>downgraded_weak</span>)]</span>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>sync</span>::<span class='ident'>Weak</span>;
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<span class='kw'>let</span> <span class='ident'>empty</span>: <span class='ident'>Weak</span><span class='op'><</span><span class='ident'>i64</span><span class='op'>></span> <span class='op'>=</span> <span class='ident'>Weak</span>::<span class='ident'>new</span>();</pre>
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</div></div><h3 class='impl'><code>impl<T> <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'><h4 id='method.upgrade' class='method'><code>fn <a href='#method.upgrade' class='fnname'>upgrade</a>(&self) -> <a class='enum' href='../../../bitflags/__core/option/enum.Option.html' title='bitflags::__core::option::Option'>Option</a><<a class='struct' href='../../../bitflags/__core/sync/struct.Arc.html' title='bitflags::__core::sync::Arc'>Arc</a><T>></code></h4>
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<div class='docblock'><p>Upgrades a weak reference to a strong reference.</p>
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<p>Upgrades the <code>Weak<T></code> reference to an <code>Arc<T></code>, if possible.</p>
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<p>Returns <code>None</code> if there were no strong references and the data was
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destroyed.</p>
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<h1 id='examples-1' class='section-header'><a href='#examples-1'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>sync</span>::<span class='ident'>Arc</span>;
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<span class='kw'>let</span> <span class='ident'>five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>new</span>(<span class='number'>5</span>);
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<span class='kw'>let</span> <span class='ident'>weak_five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>downgrade</span>(<span class='kw-2'>&</span><span class='ident'>five</span>);
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<span class='kw'>let</span> <span class='ident'>strong_five</span>: <span class='prelude-ty'>Option</span><span class='op'><</span><span class='ident'>Arc</span><span class='op'><</span>_<span class='op'>>></span> <span class='op'>=</span> <span class='ident'>weak_five</span>.<span class='ident'>upgrade</span>();</pre>
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</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><code>impl<T> <a class='trait' href='../../../bitflags/__core/ops/trait.Drop.html' title='bitflags::__core::ops::Drop'>Drop</a> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'><h4 id='method.drop' class='method'><code>fn <a href='../../../bitflags/__core/ops/trait.Drop.html#tymethod.drop' class='fnname'>drop</a>(&mut self)</code></h4>
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<div class='docblock'><p>Drops the <code>Weak<T></code>.</p>
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<p>This will decrement the weak reference count.</p>
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<h1 id='examples-2' class='section-header'><a href='#examples-2'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>sync</span>::<span class='ident'>Arc</span>;
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{
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<span class='kw'>let</span> <span class='ident'>five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>new</span>(<span class='number'>5</span>);
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<span class='kw'>let</span> <span class='ident'>weak_five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>downgrade</span>(<span class='kw-2'>&</span><span class='ident'>five</span>);
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<span class='comment'>// stuff</span>
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<span class='ident'>drop</span>(<span class='ident'>weak_five</span>); <span class='comment'>// explicit drop</span>
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}
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{
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<span class='kw'>let</span> <span class='ident'>five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>new</span>(<span class='number'>5</span>);
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<span class='kw'>let</span> <span class='ident'>weak_five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>downgrade</span>(<span class='kw-2'>&</span><span class='ident'>five</span>);
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<span class='comment'>// stuff</span>
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} <span class='comment'>// implicit drop</span></pre>
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</div></div><h3 class='impl'><code>impl<T> <a class='trait' href='../../../bitflags/__core/clone/trait.Clone.html' title='bitflags::__core::clone::Clone'>Clone</a> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'><h4 id='method.clone' class='method'><code>fn <a href='../../../bitflags/__core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T></code></h4>
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<div class='docblock'><p>Makes a clone of the <code>Weak<T></code>.</p>
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<p>This increases the weak reference count.</p>
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<h1 id='examples-3' class='section-header'><a href='#examples-3'>Examples</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>std</span>::<span class='ident'>sync</span>::<span class='ident'>Arc</span>;
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<span class='kw'>let</span> <span class='ident'>weak_five</span> <span class='op'>=</span> <span class='ident'>Arc</span>::<span class='ident'>downgrade</span>(<span class='kw-2'>&</span><span class='ident'>Arc</span>::<span class='ident'>new</span>(<span class='number'>5</span>));
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<span class='ident'>weak_five</span>.<span class='ident'>clone</span>();</pre>
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</div><h4 id='method.clone_from' class='method'><span class="since">1.0.0</span><code>fn <a href='../../../bitflags/__core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code></h4>
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</div><h3 class='impl'><code>impl<T> <a class='trait' href='../../../bitflags/__core/fmt/trait.Debug.html' title='bitflags::__core::fmt::Debug'>Debug</a> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: <a class='trait' href='../../../bitflags/__core/fmt/trait.Debug.html' title='bitflags::__core::fmt::Debug'>Debug</a> + ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'><h4 id='method.fmt' class='method'><code>fn <a href='../../../bitflags/__core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class='struct' href='../../../bitflags/__core/fmt/struct.Formatter.html' title='bitflags::__core::fmt::Formatter'>Formatter</a>) -> <a class='enum' href='../../../bitflags/__core/result/enum.Result.html' title='bitflags::__core::result::Result'>Result</a><<a class='primitive' href='https://doc.rust-lang.org/nightly/bitflags/primitive.tuple.html'>()</a>, <a class='struct' href='../../../bitflags/__core/fmt/struct.Error.html' title='bitflags::__core::fmt::Error'>Error</a>></code></h4>
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</div><h3 class='impl'><code>impl<T, U> <a class='trait' href='../../../bitflags/__core/ops/trait.CoerceUnsized.html' title='bitflags::__core::ops::CoerceUnsized'>CoerceUnsized</a><<a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><U>> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: <a class='trait' href='../../../bitflags/__core/marker/trait.Unsize.html' title='bitflags::__core::marker::Unsize'>Unsize</a><U> + ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a>, U: ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'></div><h3 class='impl'><code>impl<T> <a class='trait' href='../../../bitflags/__core/marker/trait.Sync.html' title='bitflags::__core::marker::Sync'>Sync</a> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: <a class='trait' href='../../../bitflags/__core/marker/trait.Send.html' title='bitflags::__core::marker::Send'>Send</a> + <a class='trait' href='../../../bitflags/__core/marker/trait.Sync.html' title='bitflags::__core::marker::Sync'>Sync</a> + ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'></div><h3 class='impl'><code>impl<T> <a class='trait' href='../../../bitflags/__core/marker/trait.Send.html' title='bitflags::__core::marker::Send'>Send</a> for <a class='struct' href='../../../bitflags/__core/sync/struct.Weak.html' title='bitflags::__core::sync::Weak'>Weak</a><T> <span class='where'>where T: <a class='trait' href='../../../bitflags/__core/marker/trait.Send.html' title='bitflags::__core::marker::Send'>Send</a> + <a class='trait' href='../../../bitflags/__core/marker/trait.Sync.html' title='bitflags::__core::marker::Sync'>Sync</a> + ?<a class='trait' href='../../../bitflags/__core/marker/trait.Sized.html' title='bitflags::__core::marker::Sized'>Sized</a></span></code></h3><div class='impl-items'></div></section>
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