方法一

<code class="hljs scss has-numbering">   <span class="hljs-function">dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(<span class="hljs-number">2.0</span> * NSEC_PER_SEC)</span>), <span class="hljs-function">dispatch_get_main_queue()</span>, ^{
    <span class="hljs-comment">//寫要發生的代碼；2秒以後發生</span>
});</code>

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方法二

<code class="hljs smalltalk has-numbering">  [<span class="hljs-keyword">self</span> <span class="hljs-method">performSelector:</span>&lt;<span class="hljs-array">#(發生的方法)</span>#&gt; <span class="hljs-method">withObject:</span>&lt;<span class="hljs-array">#(id)</span>#&gt; <span class="hljs-method">afterDelay:</span>&lt;<span class="hljs-array">#(幾秒以後發生)</span>#&gt;]</code>

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