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<header>Updated: 2017-06-07 21:55:59 CST +08</header>
<main>
<h1 id="golang-delete-slice-item-in-range-problem">Golang Delete Slice Item in Range Problem</h1>
<h2 id="problem">Problem</h2>
<p>When range start, it is not iterate value one by one, it is iterate by index.</p>
<p>If you modified a slice while it is in range, it will induce some problem.</p>
<h2 id="example">Example</h2>
<p>Remove char a from chars.</p>
<ul>
<li><p>Incorrect Way</p>
<pre><code class="language-go">chars := []string{"a", "a", "b"}
for i, v := range chars {
fmt.Printf("%+v, %d, %s\n", chars, i, v)
if v == "a" {
chars = append(chars[:i], chars[i+1:]...)
}
}
fmt.Printf("%+v", chars)
</code></pre>
<ul>
<li>Expected</li>
</ul>
<pre><code class="language-go">[a a b], 0, a
[a b], 0, a
[b], 0, b
Result: [b]
</code></pre>
<ul>
<li>Actual</li>
</ul>
<pre><code class="language-go">// Autual
[a a b], 0, a
[a b], 1, b
[a b], 2, b
Result: [a b]
</code></pre>
<p><a href="https://play.golang.org/p/BqMpRGlF2H">Playground</a></p></li>
<li><p>Correct Way</p>
<pre><code class="language-go">chars := []string{"a", "a", "b"}
for i := 0; i < len(chars); i++ {
if chars[i] == "a" {
chars = append(chars[:i], chars[i+1:]...)
i-- // form the remove item index to start iterate next item
}
}
fmt.Printf("%+v", chars)
</code></pre>
<p><a href="https://play.golang.org/p/z-ODXAF8xU">Playground</a></p></li>
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