Switch

The switch statement is a type of conditional used to check the value of an expression against multiple cases.

A case executes when it matches the value of the expression. When there are no matches between the case statements and the expression, the default statement executes.

var secondaryColor = "green"

switch secondaryColor {
  case "orange":
    print("Mix of red and yellow.")
  case "green":
    print("Mix of blue and yellow.")
  case "purple":
    print("Mix of red and blue.")
  default:
    print("This might not be a secondary color.")
}

// Output: Mix of blue and yellow.

Interval Matching

Intervals within a switch statement’s case provide a range of values that are checked against an expression.

let year = 1905
var artPeriod: String

switch year {
  case 1860...1885:
    artPeriod = "Impressionism"
  case 1886...1910:
    artPeriod = "Post Impressionism"
  case 1912...1935:
    artPeriod = "Expressionism"
  default:
    artPeriod = "Unknown"
}

print(artPeriod)
// Output: Post Impressionism

Compound Cases

A compound case within a switch statement is a single case that contains multiple values. These values are all checked against the switch statement’s expression and are separated by commas.

let service = "Seamless"

switch service {
  case "Uber", "Lyft":
    print("Travel")
  case "DoorDash", "Seamless", "GrubHub":
    print("Restaurant delivery")
  case "Instacart", "FreshDirect":
    print("Grocery delivery")
  default:
    print("Unknown service")
}

// Output: Restaurant delivery

Where Clause

Within a switch statement, a where clause is used to test additional conditions against an expression.

let num = 7

switch num {
  case let x where x % 2 == 0:
    print("\(num) is even.")
  case let x where x % 2 == 1:
    print("\(num) is odd.")
  default:
    print("\(num) is invalid.")
}

// Output: 7 is odd.