Golang variables

Assignment

// declare and assign variable
var name string
name = "foo"

// declare and assign var in one step
var name string = "foo"

// declare and assign variable, inferring type
name := "foo"

Constants

const myVar := "hi"       // variable that cannot be reassigned
const MyVar := "hi"       // exported variable, that cannot be reassigned

const myVar = 2           // infer constant type

const (                   // group constant assignment
    name string = "foo"
    age int = 123
)

// 'iota' will auto-increment the value of the assignment, 
// allowing you to use constants similar to an enum
//
// since the type here is inferred, comparing a variable
// with no value to the first entry will return true.
// for this reason, the first const in a iota group is generally reserved as an error
//
// ex.
//   const ( red = iota; green; blue )
//   var i int 
//   i == red // returns true
const (
    invalid = iota
    red
    green
    blue
)

There are some rules for constant:

• Constants cannot be assigned at runtime (ex. the result of a function). They must be static at compile time.
• Constants must be assigned a immutable type (ex. collections are mutable, so they cannot be constants)
• Inner scopes can declare the same constant with a new value. It will superseed the outer constant's value while working within that scope.
• If inferring a constant, it's type may take on the type of an operation it is used with. (likely best to explicitly declare type)

Type Conversion

float32(123) == 123.        // cast int as float32
string(107) == "k"          // retrieve char for 107 in ascii chart
strconv.Itoa(107) == "107"  // represent 107 as string

Introspection

fmt.Prinf("%T\n", myVar)   // print type of myVar

Mutability

Mutable

- Arrays
- Maps
- Channels
- Structs

Immutable

- Interfaces
- Booleans
- Numeric Types
- Strings
- Pointers