Creating Triangle with UIBezierPath in Swift - ios

Question

I am trying to understand how to create a triangle shape with Swift. I found this code that creates a triangle.
class TriangleLayer: CAShapeLayer {
let innerPadding: CGFloat = 30.0
override init() {
super.init()
fillColor = Colors.red.CGColor
strokeColor = Colors.red.CGColor
lineWidth = 7.0
lineCap = kCALineCapRound
lineJoin = kCALineJoinRound
path = trianglePathSmall.CGPath
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
var trianglePathSmall: UIBezierPath {
let trianglePath = UIBezierPath()
trianglePath.moveToPoint(CGPoint(x: 5.0 + innerPadding, y: 95.0)) // #1
trianglePath.addLineToPoint(CGPoint(x: 50.0, y: 12.5 + innerPadding)) // #2
trianglePath.addLineToPoint(CGPoint(x: 95.0 - innerPadding, y: 95.0)) // #3
trianglePath.closePath()
return trianglePath
}
And this code creates a shape like this
in the middle of the screen.
I tried to tweak and play around with it to understand how it works; however, at this point I realised that I got lost with the logic quite a bit. I placed the CGPoints of above triangle on an x-y axis in my head and it seems something like:
#1 x:35, y:95 #3 x:65, y:95
  #2 x:50, y: 42.5
But the triangle is created upside-down if I place the dots on the x-y axis.
What I want to achieve is what the axis tells, and I want to achieve..
. . .
<like this. not this>
. . .

Answer 1

You just have the axes in your head upside down. The coordinate system starts at 0,0 and extends right in X and down in Y.
So your points are really:
#2 x:50, y: 42.5
#1 x:35, y:95 #3 x:65, y:95
to get your desired triangle you'd have something like:
#1 x:35, y:95 #3 x:65, y:95
#2 x:50, y: 147.5

Answer 2

Result triangles
Code in swift5
//TriangleView
extension UIView {
func setRightTriangle(targetView:UIView?){
let heightWidth = targetView!.frame.size.width //you can use triangleView.frame.size.height
let path = CGMutablePath()
path.move(to: CGPoint(x: heightWidth/2, y: 0))
path.addLine(to: CGPoint(x:heightWidth, y: heightWidth/2))
path.addLine(to: CGPoint(x:heightWidth/2, y:heightWidth))
path.addLine(to: CGPoint(x:heightWidth/2, y:0))
let shape = CAShapeLayer()
shape.path = path
shape.fillColor = UIColor.blue.cgColor
targetView!.layer.insertSublayer(shape, at: 0)
}
func setLeftTriangle(targetView:UIView?){
let heightWidth = targetView!.frame.size.width
let path = CGMutablePath()
path.move(to: CGPoint(x: heightWidth/2, y: 0))
path.addLine(to: CGPoint(x:0, y: heightWidth/2))
path.addLine(to: CGPoint(x:heightWidth/2, y:heightWidth))
path.addLine(to: CGPoint(x:heightWidth/2, y:0))
let shape = CAShapeLayer()
shape.path = path
shape.fillColor = UIColor.blue.cgColor
targetView!.layer.insertSublayer(shape, at: 0)
}
func setUpTriangle(targetView:UIView?){
let heightWidth = targetView!.frame.size.width
let path = CGMutablePath()
path.move(to: CGPoint(x: 0, y: heightWidth))
path.addLine(to: CGPoint(x:heightWidth/2, y: heightWidth/2))
path.addLine(to: CGPoint(x:heightWidth, y:heightWidth))
path.addLine(to: CGPoint(x:0, y:heightWidth))
let shape = CAShapeLayer()
shape.path = path
shape.fillColor = UIColor.blue.cgColor
targetView!.layer.insertSublayer(shape, at: 0)
}
func setDownTriangle(targetView:UIView?){
let heightWidth = targetView!.frame.size.width
let path = CGMutablePath()
path.move(to: CGPoint(x: 0, y: 0))
path.addLine(to: CGPoint(x:heightWidth/2, y: heightWidth/2))
path.addLine(to: CGPoint(x:heightWidth, y:0))
path.addLine(to: CGPoint(x:0, y:0))
let shape = CAShapeLayer()
shape.path = path
shape.fillColor = UIColor.blue.cgColor
targetView!.layer.insertSublayer(shape, at: 0)
}
}

Answer 3

Swift 4.*
The easiest way of doing it by using AutoLayout:
Open your Storyboard and drag a UIView in UIViewController, position it and set the size as you wish (that's the place where the triangle will be). Set the view background to be transparent.
Create a new class, you can name it however you want (I named mine TriangleView). This will be the content of that class:
class TriangleView: UIView {
// predefined variables that can be changed
var startPoint: CGPoint = CGPoint(x: 0.0, y: 0.5)
var endPoint: CGPoint = CGPoint(x: 1.0, y: 0.5)
var firstGradientColor: UIColor = UIColor.white
var secondGradientColor: UIColor = UIColor.blue
let gradient: CAGradientLayer = CAGradientLayer()
override func draw(_ rect: CGRect) {
let height = self.layer.frame.size.height
let width = self.layer.frame.size.width
// draw the triangle
let path = UIBezierPath()
path.move(to: CGPoint(x: width / 2, y: 0))
path.addLine(to: CGPoint(x: width, y: height))
path.addLine(to: CGPoint(x: 0, y: height))
path.close()
// draw the triangle 'upside down'
// let path = UIBezierPath()
// path.move(to: CGPoint(x: 0, y: 0))
// path.addLine(to: CGPoint(x: width, y: 0))
// path.addLine(to: CGPoint(x: width / 2, y: height))
// path.close()
// add path to layer
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.lineWidth = 1.0
// Add the gradient for the view background if needed
gradient.colors = [firstGradientColor.cgColor, secondGradiendColor.cgColor]
gradient.startPoint = startPoint
gradient.endPoint = endPoint
gradient.frame = self.bounds
gradient.mask = shapeLayer
self.layer.addSublayer(gradient)
}
}
Go to your Storyboard, select the UIView and in Identity Inspector write the class name TriangleView
Enjoy your triangle! :)