Apa iku struct ing Go?

Question

IT Interview Practice · Accepted Answer

**struct** yaiku tipe komposit sing ngelompokake field-field sing gegandhengan — cara Go kanggo nemtokake tipe data khusus lan nggawe model entitas. Amarga Go ora ana kelas, struct (plus metode) yaiku cara Go nglakoni pemrograman gaya berorientasi obyek.

## Nemtokake lan nggunakake struct

```go
type Person struct {
    Name string     // exported (capitalized) → accessible from other packages
    Age  int
    email string    // unexported (lowercase) → package-private
}

// creating instances
p1 := Person{Name: "Ann", Age: 30}        // named fields (preferred — clear, order-independent)
p2 := Person{"Bob", 25, "bob@x.com"}       // positional (fragile — order matters)
var p3 Person                              // zero value: {"", 0, ""}

p1.Name          // access fields with dot notation
p1.Age = 31      // mutate
```

## Visibility field liwat kapitalisasi

```text
Capitalized field/type/func name → EXPORTED (public, usable outside the package)
lowercase name → unexported (private to the package)
```

Go nggunakake kapitalisasi, ora keyword, kanggo visibility — konvensi khas Go.

## Metode ing struct (OOP Go)

```go
// a method is a function with a RECEIVER (the struct it operates on)
func (p Person) Greet() string {           // value receiver
    return "Hi, I'm " + p.Name
}
func (p *Person) Birthday() {                // pointer receiver — can MODIFY the struct
    p.Age++
}

p1.Greet()       // "Hi, I'm Ann"
p1.Birthday()    // modifies p1 (Go auto-takes the address)
```

Metode nglampirake perilaku menyang struct liwat *receiver*. Receiver pointer (`*Person`) ngliloni metode ngowahi struct; receiver nilai mendapatake salinan.

## Struct yaiku tipe nilai

```go
p1 := Person{Name: "Ann"}
p2 := p1            // COPIES the entire struct (independent)
p2.Name = "Bob"
fmt.Println(p1.Name)   // "Ann" — unchanged (it was a copy)

// pass a pointer to share/modify
func update(p *Person) { p.Name = "X" }
```

Nugasake utawa ngepassi struct **nliyoni** (value semantics) — kanggo babagi utawa ngowahi, gunakake pointer.

## Struct tag (metadata)

```go
type User struct {
    Name  string `json:"name"`           // tags guide encoding/decoding
    Email string `json:"email,omitempty"`
}
```

Tag nglampirake metadata (digunakake dening JSON, DB, perpustakaan validasi) sing dibacok liwat reflection.

## Kenapa iku penting

Struct yaiku cara inti kanggo nggawe model data lan mbangun tipe khusus ing Go — lan digabungake karo metode, struct yaiku cara Go nglakoni pemrograman gaya berorientasi obyek (ora ana kelas).

Mahami nemtokake struct, konvensi visibility **adhedhasar kapitalisasi** (unik ing Go), **value semantics** (nugasake nyliyoni — dadi gunakake pointer kanggo babagi/owahi, kesalahan umum), metode karo receiver nilai vs pointer, lan struct tag (kanggo pemetaan JSON/DB) yaiku kadhanan pandaman kanggo meh kabeh kode Go.

Struct mundhak ing manawa-manawa — domain model, konfigurasi, payload API, struktur data — nggawakna pengetahuan sing perlu lan kanggo-kanggo kanggo ngerjani Go kanthi trep.

Nemtokake lan nggunakake struct

Visibility field liwat kapitalisasi

Metode ing struct (OOP Go)

Struct yaiku tipe nilai

Struct tag (metadata)

Kenapa iku penting

Pitakon sing gegandhengan