Type Casting or Type Conversion in Go language

Type conversion happens when we assign the value of one data type to another. Statically typed languages like C/C++, Java, provide the support for Implicit Type Conversion but Golang is different, as it doesn’t support the Automatic Type Conversion or Implicit Type Conversion even if the data types are compatible. The reason for this is the Strong Type System of the Golang which doesn’t allow to do this. For type conversion, you must perform explicit conversion.

As per Golang Specification, there is no typecasting word or terminology in Golang. If you will try to search Type Casting in Golang Specifications or Documentation, you will find nothing like this. There is only Type Conversion. In Other programming languages, typecasting is also termed as the type conversion.

What is the need for Type Conversion?

Well, if you need to take advantage of certain characteristics of data type hierarchies, then we have to change entities from one data type into another. The general syntax for converting a value val to a type T is T(val).

Example:

var geek1 int = 845

// explicit type conversion
var geek2 float64 = float64(geek1)

var geek3 int64 = int64(geek1)

var geek4 uint = uint(geek1)

// Go program to find the
// average of numbers
package main

import "fmt"

func main() {

    // taking the required
    // data into variables
    var totalsum int = 846
    var number int = 19
    var avg float32

    // explicit type conversion
    avg = float32(totalsum) / float32(number)

    // Displaying the result
    fmt.Printf("Average = %f\\n", avg)
}

Output:

Average = 44.526318

Note: As Golang has a strong type system, it doesn’t allow to mix(like addition, subtraction, multiplication, division, etc.) the numeric types in the expressions and also you are not allowed to perform an assignment between the two mixed types.

Example:

var geek1 int64 = 875

// it will give compile time error as we
// are performing an assignment between
// mixed types i.e. int64 as int type
var geek2 int = geek1

var geek3 int = 100

// it gives compile time error
// as this is invalid operation
// because types are mix i.e.
// int64 and int
var addition = geek1 + geek3