A paint pot analogy of functional programming in Swift

gistfile1.swift

typealias PositionShape = CGRect -> CAShapeLayer


func rectangle(color:UIColor) -> PositionShape {
    let shape = CAShapeLayer()
    shape.fillColor = color.CGColor
    return {
        rect in
        let path = CGPathCreateMutable()
        CGPathAddRect(path, nil, rect)
        shape.path = path
        return shape
    }
}

typealias ShapeRectangle = CGPoint -> CGRect

func startingPoint(point:CGPoint) -> ShapeRectangle {
    return {
        endPoint in
        let startPointX = point.x < endPoint.x ? point.x : endPoint.x
        let startPointY = point.y < endPoint.y ? point.y : endPoint.y
        return CGRect(x: startPointX, y: startPointY, width: abs(endPoint.x-point.x), height: abs(endPoint.y-point.y))
    }
}

// the colour has been picked
let rectPainter = rectangle(UIColor.blueColor())

// construct a CGRect from start and end points
let object = startingPoint(CGPoint(x: 150, y: 50))
let objectRect = object(CGPoint(x: 50, y: 150))

// create the CAShape layer
let rect = rectPainter(objectRect)

// add returned subview to a view
let view = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
view.layer.addSublayer(rect)
view // see added view in playground