Swift Language Advanced Operators Commutative Operators
Example
Let's add a custom operator to multiply a CGSize
func *(lhs: CGFloat, rhs: CGSize) -> CGSize{
let height = lhs*rhs.height
let width = lhs*rhs.width
return CGSize(width: width, height: height)
}
Now this works
let sizeA = CGSize(height:100, width:200)
let sizeB = 1.1 * sizeA //=> (height: 110, width: 220)
But if we try to do the operation in reverse, we get an error
let sizeC = sizeB * 20 // ERROR
But it's simple enough to add:
func *(lhs: CGSize, rhs: CGFloat) -> CGSize{
return rhs*lhs
}
Now the operator is commutative.
let sizeA = CGSize(height:100, width:200)
let sizeB = sizeA * 1.1 //=> (height: 110, width: 220)
