Zero value

Learn that every type in Go has a zero value.

Zero value

In Go every type has a zero value. When a variable is declared without an explicit value, it gets this zero value. This prevents 'undefined behaviour' issues.

For numeric types the zero value is 0, for bool false, for string "" (empty), for pointer and interface nil.

This behaviour makes Go safe; no variable starts with 'garbage'. When a new struct is created, all its fields take their zero values.

Zero value table

Zero values of common types:

int, float64: 0
bool: false
string: ""
pointer, slice, map, interface: nil
struct: each field's zero value

This table is often consulted in daily coding. Knowing zero values matters especially when checking struct fields.

Exercise Zero values

Declare var n int, var f float64, var s string and var b bool without values. Print them with fmt.Printf("%d %g %q %t\n", n, f, s, b).

Show example solution

package main

import "fmt"

func main() {
    var n int
    var f float64
    var s string
    var b bool
    fmt.Printf("%d %g %q %t\n", n, f, s, b)
}

Test yourself

What is the zero value of a string variable?
- nil
- 0
- empty string ("")
- false
Show answer

false — The zero value of string is the empty string.

Bool zero value

The zero value of a bool variable: ____

Show answer

The zero value of a bool variable: false

Match the zero values

int

0
bool

false
string

empty
pointer

nil

Next lesson: Type inference

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