英文:
Getting "bytes.Buffer does not implement io.Writer" error message
问题
我正在尝试让一个Go对象实现io.Writer接口，但是将数据写入字符串而不是文件或类似文件的对象。我以为bytes.Buffer会起作用，因为它实现了Write(p []byte)方法。然而，当我尝试以下代码时：
import "bufio"
import "bytes"
func main() {
var b bytes.Buffer
foo := bufio.NewWriter(b)
}
我得到了以下错误：
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)
我感到困惑，因为它明显实现了该接口。我该如何解决这个错误？
英文:
I'm trying to have some Go object implement io.Writer, but writes to a string instead of a file or file-like object. I thought bytes.Buffer would work since it implements Write(p []byte). However when I try this:
import "bufio"
import "bytes"
func main() {
var b bytes.Buffer
foo := bufio.NewWriter(b)
}
I get the following error:
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)
I am confused, since it clearly implements the interface. How do I resolve this error?
答案1
得分: 178
将指向缓冲区的指针传递给函数，而不是传递缓冲区本身：
import "bufio"
import "bytes"
func main() {
var b bytes.Buffer
foo := bufio.NewWriter(&b)
}
英文:
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)
}
答案2
得分: 41
你不需要使用 "bufio.NewWriter(&b)" 来创建一个 io.Writer。&b 本身就是一个 io.Writer。
英文:
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.
答案3
得分: 14
只需使用foo := bufio.NewWriter(&b)，因为bytes.Buffer实现了io.Writer接口的方式是：
func (b *Buffer) Write(p []byte) (n int, err error) {
...
}
type Writer interface {
Write(p []byte) (n int, err error)
}
它是b *Buffer，而不是b Buffer。（我也认为通过变量或其指针调用方法很奇怪，但我们不能将指针分配给非指针类型的变量。）
此外，编译器的提示不够清晰：
bytes.Buffer does not implement io.Writer (Write method has pointer receiver)
一些想法，Go使用的是值传递（Passed by value）方式，如果我们将b传递给buffio.NewWriter()，在NewWriter()中，它是一个新的b（一个新的缓冲区），而不是我们定义的原始缓冲区，因此我们需要传递地址&b。
bytes.Buffer的定义如下：
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.
}
使用值传递方式，传递的新缓冲区结构与原始缓冲区变量不同。
英文:
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.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论