Variables and Constants

Declaration and initialization of variables/constants

Before getting started

Constants

• Variables that cannot change their values

  • const in Javascript!

Untype constant

• Constants without type

  • ex)

    package main
    
    func main() {
     const name = "chloe"
    }

Type constant

• Constants with type

  • ex)

    package main
    
    func main() {
      const name string = "chloe"
    }

• Of course, since it's a constant, you cannot change the value!

  • ex)

    package main
    
    func main() {
      const name string = "chloe"
      name = "camila" // -> not possible
    }

Variables

• Literally variables (values can be changed)

  • let in Javascript!

Untype variable

• Variables without type

  • ex)

    package main
    
    import "fmt"
    
    func main() {
    
     var year = 2020
     fmt.Println(year)
    
    }

Type variable

• Variables with type

  • ex)

    package main
    
    import "fmt"
    
    func main() {
    
     var month int = 12
     // -> month := 12 (same)
    
     fmt.Println(month)
    }

Types in Go

• Go tries to figure out the type of the value you wrote

  • Because Go is a type language!

    • Must tell what the "Type is!"

      • Like Java or typescript, you need to specify the type

1. Declaring variables

1-1. Variable declaration method in Go

var variable_name variable_type

• You can set initial values right where you declare the variable

  ex)

  package main
  
  func main() {
    var num1 int = 1000
    var num2 int = 1413
  
    println("Let's do addition ~ ", num1 + num2)
  }

1-2. :=

• Called Short Assignment Statement

• Variable declaration possible without type declaration

  • Go finds the type for you!

    • Using this shorthand seems like it can be used flexibly like python!

• Can only be used inside functions!!

  ex)

  package main
  
  func main() {
   var a int = 100
   var b string = "Haha"
   c := 200
   print(b, a+c);
  }

+

Be careful that Go generates an error if you create a variable and don't use it!