How to set objects around circle correctly on UIView

Question

I've write some code to place objects around circle that locate on center of the Custom view, but it not perfectly around the circle. I don't know where of the code is wrong.

Here is the code:

func createObjectsAroundCircle() {

    let center = CGPointMake(bounds.width/2 ,bounds.height/2)
    let radius : CGFloat = 100
    let count = 20

    var angle = CGFloat(2 * M_PI)
    let step = CGFloat(2 * M_PI) / CGFloat(count)

    let circlePath = UIBezierPath(arcCenter: center, radius: radius, startAngle: CGFloat(0), endAngle:CGFloat(M_PI * 2), clockwise: true)

    let shapeLayer = CAShapeLayer()
    shapeLayer.path = circlePath.CGPath

    shapeLayer.fillColor = UIColor.clearColor().CGColor
    shapeLayer.strokeColor = UIColor.redColor().CGColor
    shapeLayer.lineWidth = 3.0

    self.layer.addSublayer(shapeLayer)

    // set objects around circle
    for var index = 0; index < count ; index++ {
        let x = cos(angle) * radius + center.x
        let y = sin(angle) * radius + center.y

        let label = UILabel()
        label.text = "\(index)"
        label.frame.origin.x = x
        label.frame.origin.y = y
        label.font = UIFont(name: "Arial", size: 20)
        label.textColor = UIColor.blackColor()
        label.sizeToFit()

        self.addSubview(label)
        angle += step 
    }
}

Answer 1

Your code is working alright, just calculation logic is wrong. You should try to set label.center instead of label.frame.origin, or

let label = UILabel()
label.text = "\(index)"
label.font = UIFont(name: "Arial", size: 20)
label.textColor = UIColor.blackColor()
label.sizeToFit()
label.frame.origin.x = x - label.frame.midX
label.frame.origin.y = y - label.frame.midY

Remember to sizeToFit() before changing frame or setting center of the label. Good Luck!

Answer 2

Swift 5

For convenience purposes, both Masa S-AiYa question logic + Fahri Azimov answer have been combined:

let center = CGPoint(x: bounds.size.width/2, y: bounds.size.width/2)
let radius: CGFloat = 100
let count = 20

let pi = Double.pi
var angle = CGFloat(2 * pi)
let step = CGFloat(2 *  pi) / CGFloat(count)

let circlePath = UIBezierPath(arcCenter: center, radius: radius, startAngle: CGFloat(0), endAngle:CGFloat(pi * 2), clockwise: true)

let shapeLayer = CAShapeLayer()
shapeLayer.path = circlePath.cgPath

shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.lineWidth = 3.0

layer.addSublayer(shapeLayer)

let font = UIFont(name: "Arial", size: 20)

// Set objects around the circle
for index in 0..<count {
    let label = UILabel()
    label.text = "\(index)"
    label.font = font
    label.textColor = .black
    // Remember to call 'sizeToFit()' before changing 'frame' or setting 'center' of the label!
    label.sizeToFit()
    
    // Position
    let x = cos(angle) * radius + center.x
    let y = sin(angle) * radius + center.y
    let midX = label.frame.x + label.frame.width / 2
    let mixY = label.frame.y + label.frame.height / 2
    
    label.frame.origin.x = x - midX
    label.frame.origin.y = y - mixY
    
    addSubview(label)
    angle += step
}