What does

print(Int("18"))

print?

Optional(18)

The Int() function returns an optional Int. The String given as an argument may not represent an Int.

Test if an optional has a value or not

if anOptional != nil {
// we have a value, we can unwrap the optional
print(anOptional!)
} else {
 // no value
}

Optional Binding

let optionalInt : Int?

if let myNumber = optionalInt {
    print(myNumber)
} else {
    print("no value for myNumber")
}

Create a simple tuple without a names for the values

let myTuple = ("John", 14)

Create a tuple with names for the values

let student = (name : "Jane", age : 18)

Access the values of a tuple by their name

let student = (name : "Jane", age : 18)
student.name // is "Jane"
student.age // is 18 

Access the values of a tuple without the name

let student = (name : "Jane", age : 18)
student.0 // is "Jane"
student.1 // is 18

Decompose a tuple into variables

let student = ("Jane", 18)
let (myName, myAge) = student
// myName is "Jane"
// myAge is 185

Tuples are used to define functions with multiple outputs.

Example:

func sinusAndCosinus(x : Double)->(sin : Double,  cos : Double) {
    return (sin(x), cos(x))
}
// sinusAndCosinus(0).sin is 0