Variable and Const

Variable

Initiate variables:

var length int

// Initiate with value
var length int = 10
var a = 10
a := 10

// Variables with same type
var length, size int

// Variable block: variables with different types
var (
  length, size int
  name string
)

// Give value to variables
var length, size int
length, size = 10, 20

// Exchange values for variables with same type
length, size = size, length

Zero value for different types:

• int: 0
• float: 0.0
• bool: false
• string: ""
• array: its items' zero value
• interface, slice, channel, map, pointer, function: nil
• struct: its items' zero value

Const

Initiation:

const a = 10

// Const block
const (
  a = 10
  b = 20
  c = 30
)

iota, anonumous variable, and Enum

iota states for the index value of current line in a const block

const (
  Sunday = iota // 0
  Monday // 1
  Tuesday // 2
  Wednesday = "n" // n
  Thursday = iota // 4, won't break incrementing
  Friday = iota // 5
  Saturday = iota //6
)

An anonumous variable could be used to skip an index for iota:

const (
  _ = iota // 0
  Mon // 1
  Tue // 2
)

To set an start value for iota:

const (
  YEAR1 = iota + 2008 // 0 + 2008 = 2008
  YEAR2 // 2009
  YEAR3 // 2010
)