iwantcoding.com
🔥 Daily 👥 Rooms 🏆 Top Log in Sign up

Basic Types

By · Reviewed & last updated · Part of Go Tutorial

Go is statically typed. Numeric types are explicit (no automatic conversion); strings are immutable byte sequences; nil is the zero value of pointers, slices, maps, channels, interfaces, and functions.

A tour of Go types

EXAMPLE
package main

import "fmt"

// Integers + floats — explicit sizes
var (
    a int     = -7
    b int32   = 123
    c uint64  = 1 << 40
    d float64 = 3.14
)

// Strings are immutable; indexing returns a byte
func strBytes() {
    s := "héllo"
    fmt.Println(len(s))          // 6 — byte length, not rune count
    fmt.Println([]byte(s)[0])    // 104
    for i, r := range s {        // ranges over runes
        fmt.Printf("%d %c\n", i, r)
    }
}

// Type conversions are explicit
func convert() {
    i := 42
    f := float64(i)
    s := fmt.Sprintf("%d", i)
    _ = f; _ = s
}

// Custom types — distinct, not aliases
type UserID int64
type Email  string

func send(_ Email) {}

func main() {
    var id UserID = 1
    var e  Email  = "ada@example.com"
    send(e)
    // send("hi")   // ERROR: untyped string isn't an Email at the call site (well, it is — but you get the idea once you wrap it in a struct)
    _ = id
}

Why it matters

Distinct named types (type UserID int64) give you type safety on primitives — mixing up a UserID and an OrderID becomes a compile error.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
var i int = 42
var f float64 = 3.14
var s string = "go"
var b bool = true
Try it Yourself »

Discussion

Loading…