The new function

Learn to allocate memory returning a pointer with new.

The new function

new(T) allocates a new zero-valued value of type T and returns its address (*T):

p := new(int)     // *int, *p == 0
*p = 42
fmt.Println(*p)   // 42

For structs, the &Type{...} form is usually preferred because the fields can be filled on the same line: u := &Urun{Ad: "Kalem"}.

Constructor functions

Go has no class constructors; instead, functions starting with New that return a pointer are written:

type Sayac struct{ n int }

func NewSayac(baslangic int) *Sayac {
    return &Sayac{n: baslangic}
}

s := NewSayac(10)
s.n++
fmt.Println(s.n)  // 11

A constructor guarantees valid starting values in one place.

Exercise Write a constructor

Write type Sayac struct{ n int } and the constructor NewSayac(baslangic int) *Sayac. Create one with s := NewSayac(10), do s.n += 5 and print s.n.

Show example solution

package main

import "fmt"

type Sayac struct{ n int }

func NewSayac(baslangic int) *Sayac {
    return &Sayac{n: baslangic}
}

func main() {
    s := NewSayac(10)
    s.n += 5
    fmt.Println(s.n)
}

Test yourself

Is it safe in Go for a function to return the address of its local variable?
- No, it becomes invalid memory
- Only with new
- It doesn't compile
- Yes; the compiler moves the value to the heap
Show answer

Yes; the compiler moves the value to the heap — Escape analysis sees the address leave the function and allocates the variable on the heap; no dangling pointer occurs as in C.

Allocate a new value

p := ____(float64)
*p = 3.5

Show answer

p := new(float64)
*p = 3.5

Expression and type

new(int)

*int (value 0)
&Urun{}

*Urun
make([]int, 3)

[]int (not a pointer)
NewSayac(10)

*Sayac

Next lesson: Pointers and functions

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies