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eBook/11.9.md
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@@ -1,20 +1,20 @@
# 11.9 <EFBFBD>սӿ<EFBFBD>
# 11.9 空接口
## 11.9.1 <EFBFBD><EFBFBD><EFBFBD><EFBFBD>
## 11.9.1 概念
**<EFBFBD>սӿڻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>С<EFBFBD>ӿ<EFBFBD>**<2A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>κη<CEBA><CEB7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD>ֲ<EFBFBD><D6B2><EFBFBD><EFBFBD>κ<EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD><EFBFBD>
**空接口或者最小接口**不包含任何方法，它对实现不做任何要求：
```go
type Any interface {}
```
<EFBFBD>κ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ͷ<EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD>˿սӿڣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Java/C#` <EFBFBD><EFBFBD> `Object` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD><EFBFBD><EFBFBD>`any` <EFBFBD><EFBFBD> `Any` <EFBFBD>ǿսӿ<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>ܺõı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><EFBFBD>
任何其他类型都实现了空接口（它不仅仅像 `Java/C#` 中 `Object` 引用类型），`any` 或 `Any` 是空接口一个很好的别名或缩写。
<EFBFBD>սӿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Java/C#` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ļ<EFBFBD><EFBFBD>ࣺ `Object` <20>࣬<EFBFBD><E0A3AC><EFBFBD>ߵ<EFBFBD>Ŀ<EFBFBD><C4BF>Ҳ<EFBFBD><D2B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
空接口类似 `Java/C#` 中所有类的基类： `Object` 类，二者的目标也很相近。
<EFBFBD><EFBFBD><EFBFBD>Ը<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>սӿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵ı<EFBFBD><EFBFBD><EFBFBD> `var val interface {}` <EFBFBD><EFBFBD><EFBFBD>κ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵<EFBFBD>ֵ<EFBFBD><EFBFBD>
可以给一个空接口类型的变量 `var val interface {}` 赋任何类型的值。
ʾ<EFBFBD><EFBFBD> 11.8 empty_interface.go<EFBFBD><EFBFBD>
示例 11.8 empty_interface.go：
```go
package main
@@ -56,16 +56,16 @@ func main() {
}
```
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
输出：
val has the value: 5
val has the value: ABC
val has the value: &{Rob Pike 55}
Type pointer to Person *main.Person
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>У<EFBFBD><EFBFBD>ӿڱ<EFBFBD><EFBFBD><EFBFBD> `val` <20><><EFBFBD><EFBFBD><EFBFBD>θ<EFBFBD><CEB8><EFBFBD>һ<EFBFBD><D2BB> `int`<EFBFBD><EFBFBD>`string` <EFBFBD><EFBFBD> `Person` ʵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֵ<EFBFBD><EFBFBD>Ȼ<EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> `type-swtich` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͡<EFBFBD>ÿ<EFBFBD><EFBFBD> `interface {}` <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><DAB4><EFBFBD>ռ<EFBFBD><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֳ<EFBFBD><D6B3><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD><CDA3><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݻ<EFBFBD><DDBB><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD><EFBFBD>ݵ<EFBFBD>ָ<EFBFBD>롣
在上面的例子中，接口变量 `val` 被依次赋予一个 `int`，`string` 和 `Person` 实例的值，然后使用 `type-swtich` 来测试它的实际类型。每个 `interface {}` 变量在内存中占据两个字长：一个用来存储它包含的类型，另一个用来存储它包含的数据或者指向数据的指针。
<EFBFBD><EFBFBD><EFBFBD><EFBFBD> emptyint_switch.go ˵<EFBFBD><EFBFBD><EFBFBD>˿սӿ<EFBFBD><EFBFBD><EFBFBD> `type-swtich` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `lambda` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>÷<EFBFBD><EFBFBD><EFBFBD>
例子 emptyint_switch.go 说明了空接口在 `type-swtich` 中联合 `lambda` 函数的用法：
```go
package main
@@ -101,21 +101,21 @@ func main() {
}
```
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
输出：
any hello is a special String!
**<EFBFBD><EFBFBD>ϰ 11.9** simple_interface3.go<EFBFBD><EFBFBD>
**练习 11.9** simple_interface3.go：
<EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><>ϰ11.2<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD> `gI` <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٽ<EFBFBD><D9BD><EFBFBD> `Simpler` <20><><EFBFBD>͵IJ<CDB5><C4B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǽ<EFBFBD><C7BD><EFBFBD>һ<EFBFBD><D2BB><EFBFBD>սӿڲ<D3BF><DAB2><EFBFBD><EFBFBD><EFBFBD>Ȼ<EFBFBD><C8BB>ͨ<EFBFBD><CDA8><EFBFBD><EFBFBD><EFBFBD>Ͷ<EFBFBD><CDB6><EFBFBD><EFBFBD>жϲ<D0B6><CFB2><EFBFBD><EFBFBD>Ƿ<EFBFBD><C7B7><EFBFBD> `Simpler` <EFBFBD><EFBFBD><EFBFBD>͡<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `main` ʹ<EFBFBD><EFBFBD> `gI` ȡ<EFBFBD><EFBFBD> `fI` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȷ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>㹻<EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD>
继续 练习11.2，在它中添加一个 `gI` 函数，它不再接受 `Simpler` 类型的参数，而是接受一个空接口参数。然后通过类型断言判断参数是否是 `Simpler` 类型。最后在 `main` 使用 `gI` 取代 `fI` 函数并调用它。确保你的代码足够安全。
## 11.9.2 <EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͨ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD><EFBFBD><EFBFBD>ͱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
## 11.9.2 构建通用类型或包含不同类型变量的数组
<EFBFBD><EFBFBD> 7.6.6 <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `int` <EFBFBD><EFBFBD><EFBFBD>顢`float` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Լ<EFBFBD> `string` <EFBFBD><EFBFBD><EFBFBD>飬<EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>أ<EFBFBD><EFBFBD>Dz<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>DZ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Լ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǣ<EFBFBD>
在 7.6.6 中我们看到了能被搜索和排序的 `int` 数组、`float` 数组以及 `string` 数组，那么对于其他类型的数组呢，是不是我们必须得自己编程实现它们？
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֪<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD><EFBFBD>ˣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͨ<EFBFBD><EFBFBD>ʹ<EFBFBD>ÿսӿڡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǹ<EFBFBD><EFBFBD>սӿڶ<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Element`<EFBFBD><EFBFBD>`type Element interface{}`
现在我们知道该怎么做了，就是通过使用空接口。让我们给空接口定一个别名类型 `Element`：`type Element interface{}`
Ȼ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵Ľṹ<EFBFBD><EFBFBD> `Vector`<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD> `Element` <20><><EFBFBD><EFBFBD>Ԫ<EFBFBD>ص<EFBFBD><D8B5><EFBFBD>Ƭ<EFBFBD><C6AC>
然后定义一个容器类型的结构体 `Vector`，它包含一个 `Element` 类型元素的切片：
```go
type Vector struct {
@@ -123,7 +123,7 @@ type Vector struct {
}
```
`Vector` <EFBFBD><EFBFBD><EFBFBD>ܷ<EFBFBD><EFBFBD>κ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD>κ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ͷ<EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD>˿սӿڣ<EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Vector` <20><><EFBFBD>ŵ<EFBFBD>ÿ<EFBFBD><C3BF>Ԫ<EFBFBD>ؿ<EFBFBD><D8BF><EFBFBD><EFBFBD>Dz<EFBFBD>ͬ<EFBFBD><CDAC><EFBFBD>͵ı<CDB5><C4B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB> `At()` <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڷ<EFBFBD><DAB7>ص<EFBFBD> `i` <EFBFBD><EFBFBD>Ԫ<EFBFBD>أ<EFBFBD>
`Vector` 里能放任何类型的变量，因为任何类型都实现了空接口，实际上 `Vector` 里放的每个元素可以是不同类型的变量。我们为它定义一个 `At()` 方法用于返回第 `i` 个元素：
```go
func (p *Vector) At(i int) Element {
@@ -131,7 +131,7 @@ func (p *Vector) At(i int) Element {
}
```
<EFBFBD>ٶ<EFBFBD>һ<EFBFBD><EFBFBD> `Set()` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>õ<EFBFBD> `i` <20><>Ԫ<EFBFBD>ص<EFBFBD>ֵ<EFBFBD><D6B5>
再定一个 `Set()` 方法用于设置第 `i` 个元素的值：
```go
func (p *Vector) Set(i int, e Element) {
@@ -139,26 +139,26 @@ func (p *Vector) Set(i int, e Element) {
}
```
`Vector` <EFBFBD>д洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ԫ<EFBFBD>ض<EFBFBD><EFBFBD><EFBFBD> `Element` <20><><EFBFBD>ͣ<EFBFBD>Ҫ<EFBFBD>õ<EFBFBD><C3B5><EFBFBD><EFBFBD>ǵ<EFBFBD>ԭʼ<D4AD><CABC><EFBFBD>ͣ<EFBFBD>unboxing<6E><67><EFBFBD><EFBFBD><EFBFBD>䣩<EFBFBD><E4A3A9>Ҫ<EFBFBD>õ<EFBFBD><C3B5><EFBFBD><EFBFBD>Ͷ<EFBFBD><CDB6>ԡ<EFBFBD>TODO<EFBFBD><EFBFBD>The compiler rejects assertions guaranteed to fail<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ͷ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD>ִ<EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
`Vector` 中存储的所有元素都是 `Element` 类型，要得到它们的原始类型（unboxing：拆箱）需要用到类型断言。TODO：The compiler rejects assertions guaranteed to fail，类型断言总是在运行时才执行，因此它会产生运行时错误。
**<EFBFBD><EFBFBD>ϰ 11.10** min_interface.go / minmain.go<EFBFBD><EFBFBD>
**练习 11.10** min_interface.go / minmain.go：
<EFBFBD><EFBFBD><EFBFBD><EFBFBD>11.7<EFBFBD>п<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Sorter` <20>ӿڣ<D3BF><DAA3><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB> `Miner` <20>ӿڲ<D3BF>ʵ<EFBFBD><CAB5>һЩ<D2BB><D0A9>Ҫ<EFBFBD>IJ<EFBFBD><C4B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Min` <EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD> `Miner` <EFBFBD><EFBFBD><EFBFBD>ͱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ļ<EFBFBD><EFBFBD>ϣ<EFBFBD>Ȼ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>㲢<EFBFBD><EFBFBD><EFBFBD>ؼ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>С<EFBFBD><EFBFBD>Ԫ<EFBFBD>ء<EFBFBD>
仿照11.7中开发的 `Sorter` 接口，创建一个 `Miner` 接口并实现一些必要的操作。函数 `Min` 接受一个 `Miner` 类型变量的集合，然后计算并返回集合中最小的元素。
## 11.9.3 <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƭ<EFBFBD><EFBFBD><EFBFBD>սӿ<EFBFBD><EFBFBD><EFBFBD>Ƭ
## 11.9.3 复制数据切片至空接口切片
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD> `myType` <EFBFBD><EFBFBD><EFBFBD>͵<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƭ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>뽫<EFBFBD><EFBFBD>Ƭ<EFBFBD>е<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݸ<EFBFBD><EFBFBD>Ƶ<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>սӿ<EFBFBD><EFBFBD><EFBFBD>Ƭ<EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ƣ<EFBFBD>
假设你有一个 `myType` 类型的数据切片，你想将切片中的数据复制到一个空接口切片中，类似：
```go
var dataSlice []myType = FuncReturnSlice()
var interfaceSlice []interface{} = dataSlice
```
<EFBFBD><EFBFBD>ϧ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>`cannot use dataSlice (type []myType) as type []interface { } in assignment`
可惜不能这么做，编译时会出错：`cannot use dataSlice (type []myType) as type []interface { } in assignment`
ԭ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD>еIJ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Dz<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>ģ<EFBFBD><EFBFBD>ο<EFBFBD>[http://golang.org/doc/go_spec.html](http://golang.org/doc/go_spec.html)<EFBFBD><EFBFBD><EFBFBD><EFBFBD>
原因是它们俩在内存中的布局是不一样的（参考[http://golang.org/doc/go_spec.html](http://golang.org/doc/go_spec.html)）。
<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> `for-range` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʽ<EFBFBD>ظ<EFBFBD><EFBFBD>ƣ<EFBFBD>
必须使用 `for-range` 语句来一个一个显式地复制：
```go
var dataSlice []myType = FuncReturnSlice()
@@ -168,11 +168,11 @@ for ix, d := range dataSlice {
}
```
## 11.9.4 ͨ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵Ľڵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݽṹ
## 11.9.4 通用类型的节点数据结构
<EFBFBD><EFBFBD>10.1<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>б<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݽṹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǵĶ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD>ֽнڵ<EFBFBD><EFBFBD>ĵݹ<EFBFBD><EFBFBD>ṹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD><EFBFBD>ڵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD>ij<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֶΡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڿ<EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD>ÿսӿ<EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֶε<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǿ<EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><EFBFBD>ͨ<EFBFBD>õĴ<EFBFBD><EFBFBD>롣<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD><EFBFBD>ִ<EFBFBD><EFBFBD>룺ͨ<EFBFBD>ö<EFBFBD><EFBFBD>塢<EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>սڵ<EFBFBD><EFBFBD><EFBFBD> `NewNode` <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݵ<EFBFBD> `SetData` <EFBFBD><EFBFBD><EFBFBD><EFBFBD>.
在10.1中我们遇到了诸如列表和树这样的数据结构，在它们的定义中使用了一种叫节点的递归结构体类型，节点包含一个某种类型的数据字段。现在可以使用空接口作为数据字段的类型，这样我们就能写出通用的代码。下面是实现一个二叉树的部分代码：通用定义、用于创建空节点的 `NewNode` 方法，及设置数据的 `SetData` 方法.
ʾ<EFBFBD><EFBFBD> 11.10 node_structures.go:
示例 11.10 node_structures.go:
```go
package main
@@ -207,11 +207,11 @@ func main() {
}
```
## 11.9.5 <EFBFBD>ӿڵ<EFBFBD><EFBFBD>ӿ<EFBFBD>
## 11.9.5 接口到接口
һ<EFBFBD><EFBFBD><EFBFBD>ӿڵ<EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD>Ը<EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>ӿڱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻҪ<EFBFBD>ײ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD>˱<EFBFBD>Ҫ<EFBFBD>ķ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD>м<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ģ<EFBFBD>ת<EFBFBD><EFBFBD>ʧ<EFBFBD>ܻᵼ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 'Go' <20><><EFBFBD>Զ<EFBFBD>̬<EFBFBD><CCAC>һ<EFBFBD>棬<EFBFBD><E6A3AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `Ruby` <EFBFBD><EFBFBD> `Python` <EFBFBD><EFBFBD>Щ<EFBFBD><EFBFBD>̬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƚϡ<EFBFBD>
一个接口的值可以赋值给另一个接口变量，只要底层类型实现了必要的方法。这个转换是在运行时进行检查的，转换失败会导致一个运行时错误：这是 'Go' 语言动态的一面，可以那它和 `Ruby` 和 `Python` 这些动态语言相比较。
<EFBFBD>ٶ<EFBFBD><EFBFBD><EFBFBD>
假定：
```go
var ai AbsInterface // declares method Abs()
@@ -223,18 +223,18 @@ pp := new(Point) // say *Point implements Abs, Sqr
var empty interface{}
```
<EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ͷ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǺϷ<EFBFBD><EFBFBD>ģ<EFBFBD>
那么下面的语句和类型断言是合法的：
```go
empty = pp // everything satisfies empty
ai = empty.(AbsInterface) // underlying value pp implements Abs()
// (runtime failure otherwise)
si = ai.(SqrInterface) // *Point has Sqr() even though AbsInterface doesn<EFBFBD><EFBFBD>t
si = ai.(SqrInterface) // *Point has Sqr() even though AbsInterface doesn’t
empty = si // *Point implements empty set
// Note: statically checkable so type assertion not necessary.
```
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>õ<EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ӣ<EFBFBD>
下面是函数调用的一个例子：
```go
type myPrintInterface interface {
@@ -246,10 +246,10 @@ func f3(x myInterface) {
}
```
`x` ת<EFBFBD><EFBFBD>Ϊ `myPrintInterface` <EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD>̬<EFBFBD>ģ<EFBFBD>ֻҪ `x` <20>ĵײ<C4B5><D7B2><EFBFBD><EFBFBD>ͣ<EFBFBD><CDA3><EFBFBD>̬<EFBFBD><CCAC><EFBFBD>ͣ<EFBFBD><CDA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> `print` <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>þͿ<C3BE><CDBF><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>С<EFBFBD>
`x` 转换为 `myPrintInterface` 类型是完全动态的：只要 `x` 的底层类型（动态类型）定义了 `print` 方法这个调用就可以正常运行。
## <EFBFBD><EFBFBD><EFBFBD><EFBFBD>
## 链接
- [Ŀ¼](directory.md)
- <EFBFBD><EFBFBD>һ<EFBFBD>ڣ<EFBFBD>[<EFBFBD>ڶ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ӣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д](11.8.md)
- <EFBFBD><EFBFBD>һ<EFBFBD>ڣ<EFBFBD>[<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](11.10.md)
- [目录](directory.md)
- 上一节：[第二个例子：读和写](11.8.md)
- 下一节：[反射包](11.10.md)