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<meta property="og:description" content="下面的代码均省略包导入和主函数，只列出说明代码 1：不能为非本地类型申明方法 func (i int) add (j int) int { return i + j } 如果运行上面的代码，会报错cannot define new methods on non-local type int，正确的写法是先将 int 类型申明为本地类型 type LocalInt int func (i *LocalInt) add (j LocalInt) LocalInt { return *i + j } 之所以申明为指针类型接受者，是为了方便后面讲解 2：类型字面量，不能直接调用指针接受者方法，必须先申明变量 LocalInt(12).add(LocalInt …" />
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<meta name="twitter:description" content="下面的代码均省略包导入和主函数，只列出说明代码 1：不能为非本地类型申明方法 func (i int) add (j int) int { return i + j } 如果运行上面的代码，会报错cannot define new methods on non-local type int，正确的写法是先将 int 类型申明为本地类型 type LocalInt int func (i *LocalInt) add (j LocalInt) LocalInt { return *i + j } 之所以申明为指针类型接受者，是为了方便后面讲解 2：类型字面量，不能直接调用指针接受者方法，必须先申明变量 LocalInt(12).add(LocalInt …">
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Go 的方法申明总结
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<p><em>下面的代码均省略包导入和主函数，只列出说明代码</em></p>
<h4>1：不能为非本地类型申明方法</h4>
<div class="highlight"><pre><span></span><span class="kd">func</span> <span class="p">(</span><span class="nx">i</span> <span class="kt">int</span><span class="p">)</span> <span class="nx">add</span> <span class="p">(</span><span class="nx">j</span> <span class="kt">int</span><span class="p">)</span> <span class="kt">int</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">i</span> <span class="o">+</span> <span class="nx">j</span>
<span class="p">}</span>
</pre></div>
<p><em>如果运行上面的代码，会报错<code>cannot define new methods on non-local type int</code>，正确的写法是先将 int 类型申明为本地类型</em></p>
<div class="highlight"><pre><span></span><span class="kd">type</span> <span class="nx">LocalInt</span> <span class="kt">int</span>
<span class="kd">func</span> <span class="p">(</span><span class="nx">i</span> <span class="o">*</span><span class="nx">LocalInt</span><span class="p">)</span> <span class="nx">add</span> <span class="p">(</span><span class="nx">j</span> <span class="nx">LocalInt</span><span class="p">)</span> <span class="nx">LocalInt</span> <span class="p">{</span>
<span class="k">return</span> <span class="o">*</span><span class="nx">i</span> <span class="o">+</span> <span class="nx">j</span>
<span class="p">}</span>
</pre></div>
<blockquote>
<p>之所以申明为指针类型接受者，是为了方便后面讲解</p>
</blockquote>
<h3>2：类型字面量，不能直接调用指针接受者方法，必须先申明变量</h3>
<div class="highlight"><pre><span></span><span class="nx">LocalInt</span><span class="p">(</span><span class="mi">12</span><span class="p">).</span><span class="nx">add</span><span class="p">(</span><span class="nx">LocalInt</span><span class="p">(</span><span class="mi">12</span><span class="p">))</span>
</pre></div>
<p><em>运行上面的代码，会如下错</em></p>
<div class="highlight"><pre><span></span><span class="c1"># command-line-arguments</span>
./test.go:28:17: cannot call pointer method on LocalInt<span class="o">(</span><span class="m">12</span><span class="o">)</span>
./test.go:28:17: cannot take the address of LocalInt<span class="o">(</span><span class="m">12</span><span class="o">)</span>
</pre></div>
<p><em>应先申明变量</em></p>
<div class="highlight"><pre><span></span><span class="nx">i</span> <span class="o">:=</span> <span class="nx">LocalInt</span><span class="p">(</span><span class="mi">12</span><span class="p">)</span>
<span class="nx">i</span><span class="p">.</span><span class="nx">add</span><span class="p">(</span><span class="nx">LocalInt</span><span class="p">(</span><span class="mi">12</span><span class="p">))</span>
</pre></div>
<h3>3：go为强类型，相关类型不能混用</h3>
<div class="highlight"><pre><span></span><span class="nx">i</span> <span class="o">:=</span> <span class="mi">12</span>
<span class="nx">i</span><span class="p">.</span><span class="nx">add</span><span class="p">(</span><span class="nx">LocalInt</span><span class="p">(</span><span class="mi">12</span><span class="p">))</span>
</pre></div>
<p><em>虽然 LocalInt 和 int 类型表现一致，但它们仍不是同一种类型，因此会报错<code>i.add undefined (type int has no field or method add)</code></em></p>
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