[Swift] Var, Let and Tuple

var

• Values assigned to variables can be changed

  var myVar = 10 // :Int
  var x = 0.0, y = 0.0, z = 0.0
  

let

• Once assigned, it cannot be changed later

  let myLet = 10
  

tyoe annotation and tyoe inference

var userId : Int = 10 // Int is type annotation
var pi = 3.14 // Double type inference

Tuple

• To temporarily bind multiple values to a single object

  let myTuple = (10, 12.1, "Hi")
  var getTuple = myTuple.2
  print(getTuple)
  // Hi
  

• Extract all values in the Tuple and assign them to variables or constants

  let myTuple = (10, 12.1, "Hi")
  let (myInt, myFloat, myString) = myTuple
  print(myFloat)
  // 12.1
  

• _ ignore the value

  let myTuple = (10, 12.1, "Hi")
  let (myInt, _, myString) = myTuple
  

• When creating a Tuple, you can assign a name to each value.

  let myTuple = (id: 10, length: 12.1, message: "Hi")
  print(myTuple.message);
  // Hi