问一个关于 bytes.Buffer 的问题

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This topic created in 2518 days ago, the information mentioned may be changed or developed.

```
buf := new(bytes.Buffer)
w := zip.NewWriter(buf)
defer w.Close()
```
这样没问题
```
var buf bytes.Buffer
w := zip.NewWriter(buf)
defer w.Close()
```
这样就报
cannot use buf (type bytes.Buffer) as type io.Writer in argument to zip.NewWriter:
bytes.Buffer does not implement io.Writer (Write method has pointer receiver)
想问的是为什么 new 出来的就有 io.Writer 接口，局部变量就没有？

2 replies

fork

Jul 7, 2019

new 创建的是指针类型*bytes.Buffer, 只有指针类型实现了 io.Writer 接口

46fo

Jul 8, 2019

@fork 3Q。我试过
var buf bytes.Buffer
w := zip.NewWriter(&buf)
defer w.Close()
这样就没问题了。