Property observers respond to changes to a property’s value.
var myProperty = 5 {
willSet {
print("Will set to \(newValue). It was previously \(myProperty)")
}
didSet {
print("Did set to \(myProperty). It was previously \(oldValue)")
}
}
myProperty = 6
// prints: Will set to 6, It was previously 5
// prints: Did set to 6. It was previously 5