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<!DOCTYPE html>
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go 语言类型推断 - 搁羽念风
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<h1 class="entry-title">go 语言类型推断</h1>
<p class="meta"><time datetime="2019-01-25T00:20:13+08:00" pubdate data-updated="true">2019/1/25</time></p>
</header>
<div class="entry-content">
<h2 id="toc_0">执行之前动态确保一个结构体拥有某个方法</h2>
<blockquote>
<p>类型断言之后,只能使用接口里定义的方法<br/>
比如 Runner 实际上有 <code>SetId</code> 和 <code>GetId</code> 两个方法<br/>
但是 动态约束了 <code>demo.(interface{SetId(int64)})</code> 之后<br/>
就只能使用<code>SetId</code> 这个方法了</p>
</blockquote>
<pre class="line-numbers"><code class="language-go">package main
import (
"fmt"
)
type Runner struct {
Num int64
}
func (self *Runner) SetId(num int64) {
self.Num = num
fmt.Println(self.Num)
}
func (self *Runner) GetId() int64 {
return self.Num
}
func main() {
var demo interface{} = new(Runner)
demo.(interface {
SetId(int64)
}).SetId(134)
}
</code></pre>
<h2 id="toc_1">利用类型断言,确定变量的类型</h2>
<blockquote>
<p>可以根据不同的类型,进行不同的操作</p>
</blockquote>
<pre class="line-numbers"><code class="language-go">package main
import (
"fmt"
)
func checkType(in interface{}) {
switch value := in.(type) {
case int:
fmt.Println("int", value)
case string:
fmt.Println("string", value)
default:
fmt.Println("unknow", value)
}
}
func main() {
ccc := 134
checkType(ccc)
ddd := "133"
checkType(ddd)
eee := []string{"d", "d", "e"}
checkType(eee)
}
</code></pre>
<h2 id="toc_2">函数作为参数传递</h2>
<blockquote>
<p>函数作为参数传入 并且 被调函数, 参数类型为 interface{}时<br/>
该函数是无法执行的<br/>
将其进行类型转换,即可执行</p>
</blockquote>
<pre class="line-numbers"><code class="language-go">package main
import "fmt"
type Handler func(int, string, int) // 定义一个函数类型
func demo(a int, b string, c int) {
fmt.Println(a, b, c)
}
func check(in interface{}) {
in.(Handler)(112, "ccc", 222)
}
func main() {
check(Handler(demo))
}
</code></pre>
<h2 id="toc_3">类型断言</h2>
<pre class="line-numbers"><code class="language-go">x := "hello world"
if v, ok := interface{}(x).(string); ok { // interface{}(x):把 x 的类型转换成 interface{}
fmt.Println(v)
}
</code></pre>
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