嵌入式接口 [英] Embedded Interface

问题描述

Go对我来说还很新，我很惊讶无法使用嵌入式接口的子类型。
这里是一个小例子来解释我的意思：

pre $ func test（sl bufio.ReadWriter）{
//不能在函数参数
readStuff（sl）
[...]
writeStuff（sl）中使用类型为bufio.Reader的sl（类型为bufio.ReadWriter）//同类错误
}

func readStuff（sl bufio.Reader）{
[...]
}

由于每个接口都有相同的内存布局，ReadWriter是一个Reader和一个Writer，所以我希望这个代码能够工作。
我尝试将接口类型转换为：

  readStuff（sl。（buffio.Reader））
  

但它也不起作用。所以我有两个问题：

• 为什么它不起作用？
他们是不同的类型。但是， bufio.ReadWriter 包含一个指向 bufio.Reader 类型和一个 bufio.Writer 键入为其结构的元素。所以传递正确的应该很容易。试试这个：



  func test（sl bufio.ReadWriter）{
 readStuff（sl.Reader）
 [...] 
 writeStuff（sl.Writer）
} 
 
 //将此bufio.Reader更改为指针接收器
 func readStuff（sl * bufio。阅读器）{
 [...] 
} 
  




I'm still quite new to Go and I was surprised to not be able to use the subtype of an embedded interface. Here is a small example to explain what I mean:

func test(sl bufio.ReadWriter){
    // cannot use sl(type bufio.ReadWriter) as type bufio.Reader in function argument
    readStuff(sl) 
    [...]
    writeStuff(sl) // same kind of error
}

func readStuff(sl bufio.Reader){
    [...]
}

As every interface have the same memory layout and ReadWriter is a Reader and a Writer, I was expecting this code to work. I did try to convert the interface type with:

readStuff(sl.(buffio.Reader))

But it doesn't work either. So I've got two questions:

• Why doesn't it work?
• What's the go philosophy about that problem?

解决方案

They're different types. However, a bufio.ReadWriter contains a pointer to both a bufio.Reader type and a bufio.Writer type as elements of its struct. So passing the correct one should be easy enough. Try this:

func test(sl bufio.ReadWriter){
    readStuff(sl.Reader)
    [...]
    writeStuff(sl.Writer)
}

// Changed this bufio.Reader to a pointer receiver
func readStuff(sl *bufio.Reader) {
    [...]
}

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