Variables¶

There are 3 ways to declare variables in go.

package main

import (
        "fmt"
)

func main() {

        var i int
        i = 42
        i = 27
        fmt.Println(i)

        var j int = 42
        fmt.Println(j)

        k := 12
        fmt.Println(k)

}

Another method is to declare variables at package level.

var l float32 = 56

func main() {
    fmt.Println(l)
}

We can also define a block of variables.

var (                                         
        actorName       string = "Elisabeth Sladen"
        companion       string = "Sarah Jane Smith"
        doctorNumber    int    = 3
        season          int    = 11
)

Redeclare variables¶

In go we can't really redeclare variables, but we can shadow them. Which means, if the variable is declared in a higher level scope, we can redeclare it in a lower level scope.

var l float32 = 56

func main() {
    fmt.Println(l)
    var l int = 42
    fmt.Println(l)

    var m int = 26
    // var m float32 = 12 -- will throw an error
}

The output will be

56
42

Other interesting things about variables¶

• They always have to be used.

When you are declaring and variable that is not used, the compiler will throw an error:

$variable declared and not used

• Visibility

  • lower case first letter variables are used for package scope
    • any file at that package can access the variable
  • upper case first letter to export
    • exported from the package, globally visible
  • no private scope
    • you can't scope variable to the scope itself, but you can declare it in a block and scope to it.

• Naming conventions

  • Pascal or camelCase
    • Capitalize acronyms (HTTP, URL)
  • As short as reasonable
    • longer names for longer lives

• Conversion

  • destinationType(variable)
  • use strconv package for strings

j = float32(l)
fmt.Printf("%v, %T\n", j, j)

l = int(j)
fmt.Printf("%v, %T\n", l, l)

var m int = 42
fmt.Printf("%v, %T\n", m, m)

var n string
n = string(m)
fmt.Printf("%v, %T\n", n, n) // will result in `*`

n = strconv.Itoa(m)
fmt.Printf("%v, %T\n", n, n) // will result to `42`

42, float32
42, int
42, int
*, string
42, string