wiki/content/20200928193245-embedding.md

date	id	title
2020-09-28	8f08356d-b0dc-465b-b7f5-5522b5133916	Golang Embedding

Description

Embedding is Gos answer to subclasses. There's one caveat:

There's an important way in which embedding differs from subclassing. When we embed a type, the methods of that type become methods of the outer type, but when they are invoked the receiver of the method is the inner type, not the outer one.

Interfaces

type Reader interface {
    Read(p []byte) (n int, err error)
}

type Writer interface {
    Write(p []byte) (n int, err error)
}

type ReadWriter interface {
    Reader
    Writer
}

ReadWriter "extends" Reader & Writer in the example above.

Structs

type ReadWriter struct {
    *Reader  // *bufio.Reader
    *Writer  // *bufio.Writer
}

func (rw *ReadWriter) Read(p []byte) (n int, err error) {
    return rw.reader.Read(p)
}