Type Conversion in

About Type Conversion

Go requires explicit conversion between different types. For example, this causes a compiler error:

var x int = 42
var f float64 = x // compiler error x is an int not a float64

Converting between types (also know as type casting) is done via a function with the name of the type to convert to. A value v is converted to type T using T(v). For example, to convert an int to a float64 you would need to do the following:

var x int = 42 // x has type int
f := float64(x) // f has type float64 (ie. 42.0)

The same applies to any custom types:

type Id int
var number int = 121 // number has type int
userId := Id(number) // userId now has type Id

Converting between primitive types and strings

There is a strconv package for converting between primitive types (like int) and string.

import "strconv"

var intString string = "42"
var i, err = strconv.Atoi(intString)

var number int = 12
var s string = strconv.Itoa(number)

WARNING: using the standard casting method does not have this behavior. For example:

var num int = 65
str := string(num) // str is now "A" not "65"

Here are some of the other common conversion methods: