# 切片 slice 并不是數組或數組指針。它通過內部指針和相關屬性引用數組片段，以實現變長方案 ``` <pre class="calibre13">``` <span class="token5">1.</span> 切片：切片是數組的一個引用，因此切片是引用類型。但自身是結構體，值拷貝傳遞。 <span class="token5">2.</span> 切片的長度可以改變，因此，切片是一個可變的數組。 <span class="token5">3.</span> <span class="token3">切片遍歷方式和數組一樣，可以用len</span><span class="token1">(</span><span class="token1">)</span>求長度。表示可用元素數量，讀寫操作不能超過該限制。 <span class="token5">4.</span> cap可以求出slice最大擴張容量，不能超出數組限制。<span class="token5">0</span> <span class="token"><=</span> <span class="token3">len</span><span class="token1">(</span>slice<span class="token1">)</span> <span class="token"><=</span> <span class="token3">len</span><span class="token1">(</span>array<span class="token1">)</span>，其中array是slice引用的數組。 <span class="token5">5.</span> 切片的定義：<span class="token2">var</span> 變量名 <span class="token1">[</span><span class="token1">]</span>類型，比如 <span class="token2">var</span> str <span class="token1">[</span><span class="token1">]</span>string <span class="token2">var</span> arr <span class="token1">[</span><span class="token1">]</span>int。 <span class="token5">6.</span> 如果 slice <span class="token">==</span> nil，那么 len、cap 結果都等于 <span class="token5">0</span>。 ``` ``` ## 數組和切片用法不同的地方 ### 初始化 ``` <pre class="calibre13">``` 數組：是同一種數據類型的固定長度的序列 數組定義：<span class="token2">var</span> a <span class="token1">[</span>len<span class="token1">]</span>int ``` ``` ``` <pre class="calibre13">``` 聲明切片： <span class="token2">var</span> s1 <span class="token1">[</span><span class="token1">]</span>int s2 <span class="token1">:</span><span class="token">=</span> <span class="token1">[</span><span class="token1">]</span>int<span class="token1">{</span><span class="token1">}</span> <span class="token2">var</span> s3 <span class="token1">[</span><span class="token1">]</span>int <span class="token">=</span> <span class="token3">make</span><span class="token1">(</span><span class="token1">[</span><span class="token1">]</span>int<span class="token1">,</span> <span class="token5">0</span><span class="token1">)</span> <span class="token2">var</span> s4 <span class="token1">[</span><span class="token1">]</span>int <span class="token">=</span> <span class="token3">make</span><span class="token1">(</span><span class="token1">[</span><span class="token1">]</span>int<span class="token1">,</span> <span class="token5">0</span><span class="token1">,</span> <span class="token5">0</span><span class="token1">)</span> ``` ``` ``` <pre class="calibre14">``` <span class="token6">// 5.從數組切片</span> arr <span class="token1">:</span><span class="token">=</span> <span class="token1">[</span><span class="token5">5</span><span class="token1">]</span>int<span class="token1">{</span><span class="token5">1</span><span class="token1">,</span> <span class="token5">2</span><span class="token1">,</span> <span class="token5">3</span><span class="token1">,</span> <span class="token5">4</span><span class="token1">,</span> <span class="token5">5</span><span class="token1">}</span> <span class="token2">var</span> s6 <span class="token1">[</span><span class="token1">]</span>int <span class="token6">// 前包后不包</span> s6 <span class="token">=</span> arr<span class="token1">[</span><span class="token5">1</span><span class="token1">:</span><span class="token5">4</span><span class="token1">]</span> ``` ```