Occasionally you may want to use the same tuple type in multiple places throughout your code. This can quickly get messy, especially if your tuple is complex:
// Define a circle tuple by its center point and radius
let unitCircle: (center: (x: CGFloat, y: CGFloat), radius: CGFloat) = ((0.0, 0.0), 1.0)
func doubleRadius(ofCircle circle: (center: (x: CGFloat, y: CGFloat), radius: CGFloat)) -> (center: (x: CGFloat, y: CGFloat), radius: CGFloat) {
return (circle.center, circle.radius * 2.0)
}
If you use a certain tuple type in more than one place, you can use the [typealias](<https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/doc/uid/TP40014097-CH34-ID361>)
keyword to name your tuple type.
// Define a circle tuple by its center point and radius
typealias Circle = (center: (x: CGFloat, y: CGFloat), radius: CGFloat)
let unitCircle: Circle = ((0.0, 0.0), 1)
func doubleRadius(ofCircle circle: Circle) -> Circle {
// Aliased tuples also have access to value labels in the original tuple type.
return (circle.center, circle.radius * 2.0)
}
If you find yourself doing this too often, however, you should consider using a [struct](<http://stackoverflow.com/documentation/swift/255/structs>)
instead.