I was looking at NewScanner in the official go docs and it mentions the parameter to be passed to bufio.NewScanner should be of type io.Reader. However, the following works for me:
file, err := os.Open("filename")
scanner := bufio.NewScanner(file)
The same can be seen for os.Stdin as well. Given this what is the difference between os.File, os.Stdin and io.Reader ? Are they interchangeable?
分享 This is because bufio.NewScanner has io.Reader as an argument.
func NewScanner(r io.Reader) *Scanner
and io.Reader is the interface that wraps the basic Read method.
type Reader interface {
Read(p []byte) (n int, err error)
}
From the os package in Golang:
Open opens the named file for reading. If successful, methods on the returned file can be used for reading; the associated file descriptor has mode O_RDONLY. If there is an error, it will be of type *PathError.
func Open(name string) (file *File, err error)
The returned value *os.File implements io.Reader.
So whetever implements Reader interface can be passed as an argument to any method has io.Reader as an argument.
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