How to accept either a CGFloat or an Array of CGFloats as a function argument?

Question

I have an auto layout convenience function which stacks views on top of each other. For my spacing parameter, I would like to allow:

• zero spacing between views
• or a single CGFloat (all views spaced evenly)
• or an array of CGFloats (different spaces between views)

However, I'm not sure how to define this argument.

// Ambiguous
func myconstrainer(_ views : [UIView], spacing : CGFloat = 0){}
func myconstrainer(_ views : [UIView], spacing : [CGFloat]? = nil){}

// Messy
func myconstrainer(_ views : [UIView], spacingA : CGFloat = 0, spacingB: [CGFloat]? = nil){}

Answer 1

You can also try variable number of arguments like this:

func myconstrainer(_ views: [UIView], spacing: CGFloat...) {
    myconstrainer(views, spacing: spacing)
}

and provide a simple overload to work with arrays as well:

func myconstrainer(_ views: [UIView], spacing: [CGFloat]) {
    // Implementation...
}

As such, you won't need to put a single element in brackets when using even spacing.

Call sites:

myconstrainer([view1, view2, view3])
myconstrainer([view1, view2, view3], spacing: 123)
myconstrainer([view1, view2, view3], spacings: 1, 2, 3)
myconstrainer([view1, view2, view3], spacings: [1, 2, 3])

Some non-obvious notes:

• the default case is nicely covered by calling CGFloat... with zero arguments;
• and, since this argument is actually an array, we can forward it to the other method without brackets.