Struct embedding

Learn to embed one struct inside another.

Struct embedding

Go has no inheritance; instead a struct embeds another struct. The embedded struct's fields and methods become directly accessible through the outer struct:

type Kisi struct {
    Ad  string
    Yas int
}

type Calisan struct {
    Kisi          // no field name: embedded
    Departman string
}

c := Calisan{Kisi{"Ada", 36}, "Ar-Ge"}
fmt.Println(c.Ad, c.Departman)  // Ada Ar-Ge

Composition, not inheritance

Embedding isn't an "is-a" relationship but a "has-a" one: a Calisan can't be used where a Kisi value is expected. If fields share a name, the outer struct's field wins; the embedded one is reached through the full path. This clear rule avoids the complexity of deep inheritance hierarchies.

Exercise Employee record

Write Kisi (Ad string, Yas int) and Calisan (Departman string), which embeds it. Create c := Calisan{Kisi{"Ada", 36}, "Ar-Ge"}, do c.Yas++ and print c.Ad, c.Yas and c.Departman.

Show example solution

package main

import "fmt"

type Kisi struct {
    Ad  string
    Yas int
}

type Calisan struct {
    Kisi
    Departman string
}

func main() {
    c := Calisan{Kisi{"Ada", 36}, "Ar-Ge"}
    c.Yas++
    fmt.Println(c.Ad, c.Yas, c.Departman)
}

Test yourself

What is the difference between <code>c.Ad</code> and <code>c.Kisi.Ad</code>?
- c.Ad returns empty
- None; c.Ad is shorthand for c.Kisi.Ad
- c.Ad is a copy
- c.Kisi.Ad doesn't compile
Show answer

None; c.Ad is shorthand for c.Kisi.Ad — Embedded fields are "promoted"; the full path c.Kisi.Ad is always valid too.

Embedded field

type Ogretmen struct {
    ____
    Brans string
}

Show answer

type Ogretmen struct {
    Kisi
    Brans string
}

Concept

Embedding

Has-a relationship
c.Ad

Promoted field
c.Kisi.Ad

Full path
Inheritance

Not in Go

Next lesson: Struct and pointer

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