What Is the io.Writer Interface and How to Use It

The io.Writer interface defines a single method, Write(p []byte) (n int, err error), that any type can implement to accept byte data. It is used by Go's standard library to write data to files, networks, or memory buffers without needing to know the specific destination type.

import (
	"io"
	"os"
)

func writeData(w io.Writer, data []byte) error {
	_, err := w.Write(data)
	return err
}

// Usage: writeData(os.Stdout, []byte("Hello"))

The Write method takes a byte slice, writes it to the underlying destination, and returns the number of bytes written and any error encountered.

The io.Writer interface is a standard contract in Go that allows any program to send data to a destination like a file, a network connection, or the screen. It works like a universal adapter, letting you write code that handles data without worrying about where it is going. This makes your code flexible and reusable across different parts of your application.