Using a typealias to name your tuple type

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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 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 instead.

Found a mistake? Have a question or improvement idea? Let me know.

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