英文:
Wrap io.PipeReader to store progress
问题
我想要在io.Pipe中跟踪进度。我设计了以下的结构体ProgressPipeReader，它包装了io.PipeReader，并将进度以字节的形式存储在ProgressPipeReader.progress中：
type ProgressPipeReader struct {
io.PipeReader
progress int64
}
func (pr *ProgressPipeReader) Read(data []byte) (int, error) {
n, err := pr.PipeReader.Read(data)
if err == nil {
pr.progress += int64(n)
}
return n, err
}
不幸的是，我似乎无法使用它来包装io.PipeReader。以下代码片段：
pr, pw := io.Pipe()
pr = &ProgressPipeReader{PipeReader: pr}
会产生错误：
cannot use pr (type *io.PipeReader) as type io.PipeReader in field value
有什么提示吗？
英文:
I would like to keep track of the progress in an io.Pipe. I came up with the following struct ProgressPipeReader which wraps io.PipeReader, storing the progress in bytes inside ProgressPipeReader.progress:
type ProgressPipeReader struct {
io.PipeReader
progress int64
}
func (pr *ProgressPipeReader) Read(data []byte) (int, error) {
n, err := pr.PipeReader.Read(data)
if err == nil {
pr.progress += int64(n)
}
return n, err
}
Unfortunately, I can't seem to use it to wrap an io.PipeReader. The following snippet
pr, pw := io.Pipe()
pr = &ProgressPipeReader{PipeReader: pr}
yields the error
cannot use pr (type *io.PipeReader) as type io.PipeReader in field value
Any hints?
答案1
得分: 2
根据错误描述，你试图将*io.PipeReader的值存储在io.PipeReader字段中。你可以通过更新结构体定义为正确的类型来解决这个问题：
type ProgressPipeReader struct {
*io.PipeReader
progress int64
}
英文:
As the error describes, you are trying to store a *io.PipeReader value in a io.PipeReader field. You can fix this by updating your struct definition to the correct type:
type ProgressPipeReader struct {
*io.PipeReader
progress int64
}
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