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:

Method	Purpose
ParseBool	Convert string to bool
FormatBool	Convert bool to string
ParseFloat	Convert string to float
FormatFloat	Convert float to string
ParseInt	Convert string to int
FormatInt	Convert int to string

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Originally from Exercism go concepts