获取“ byte.Buffer 未实现 io.Writer”错误消息

我正在尝试一些 Go 对象实现。但是写入字符串而不是文件或类似文件的对象。我认为 bytes.Buffer会工作，因为它实现 Write(p []byte)。然而，当我尝试这样做时:

import "bufio"
import "bytes"


func main() {
var b bytes.Buffer
foo := bufio.NewWriter(b)
}

我得到以下错误:

cannot use b (type bytes.Buffer) as type io.Writer in function argument:
bytes.Buffer does not implement io.Writer (Write method has pointer receiver)

我很困惑，因为它清楚地实现了接口。我如何解决这个错误？

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小开
最佳答案

Pass a pointer to the buffer, instead of the buffer itself:

import "bufio"
import "bytes"


func main() {
var b bytes.Buffer
foo := bufio.NewWriter(&b)
}
小开 
package main


import "bytes"
import "io"


func main() {
var b bytes.Buffer
_ = io.Writer(&b)
}

You don't need use "bufio.NewWriter(&b)" to create an io.Writer. &b is an io.Writer itself.

小开

Just use

foo := bufio.NewWriter(&b)

Because the way bytes.Buffer implements io.Writer is

func (b *Buffer) Write(p []byte) (n int, err error) {
...
}
// io.Writer definition
type Writer interface {
Write(p []byte) (n int, err error)
}

It's b *Buffer, not b Buffer. (I also think it is weird for we can call a method by a variable or its pointer, but we can't assign a pointer to a non-pointer type variable.)

Besides, the compiler prompt is not clear enough:

bytes.Buffer does not implement io.Writer (Write method has pointer receiver)

Some ideas, Go use Passed by value, if we pass b to buffio.NewWriter(), in NewWriter(), it is a new b (a new buffer), not the original buffer we defined, therefore we need pass the address &b.

bytes.Buffer is defined as:

type Buffer struct {
buf       []byte   // contents are the bytes buf[off : len(buf)]
off       int      // read at &buf[off], write at &buf[len(buf)]
bootstrap [64]byte // memory to hold first slice; helps small buffers avoid allocation.
lastRead  readOp   // last read operation, so that Unread* can work correctly.
}

using passed by value, the passed new buffer struct is different from the origin buffer variable.


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