ios - Possible to get view size from within a class? (Swift)

Question

If a subview of class MyClass is added to another view:

secondView = MyClass() 
mainView.addSubview(secondView)

is it possible to get the subview's dimensions from within the class?

secondView = MyClass()
mainView.addSubview(secondView)

class MyClass: UIView {
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() -> Void {
        // do whatever the view will need to show
        // *** can I get the view's dimensions here? <----------------------***
        // e.g., draw a diagonal line 
        //  from top left corner to bottom right corner

        // self.bounds and self.frame return (0, 0, 0, 0) here
    }
}

Or do they need to be passed in somehow from the view creating it (mainView)?

question from:https://stackoverflow.com/questions/65713480/possible-to-get-view-size-from-within-a-class-swift

Answer 1

You cannot get a view's size reliably within init. A view's size can change. Therefore you should either do any drawing you need in drawrect, or if you are using CALAyer, resize your layer in layoutSubviews where you will have the bounds of your view and you can then use that to set the frame of your sublayer or subviews. https://developer.apple.com/documentation/uikit/uiview/1622482-layoutsubviews https://developer.apple.com/documentation/uikit/uiview/1622529-drawrect Here is a playground with a simple line example.

import UIKit
import Combine
import PlaygroundSupport

final class XView: UIView {
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        UIColor.red.setStroke()
        let path = UIBezierPath()
        path.lineWidth = 10
        path.move(to: rect.origin)
        path.addLine(to: .init(x: rect.maxX, y: rect.maxY))
        path.stroke()
    }
}
let v = XView()
v.frame = .init(origin: .zero, size: .init(width: 300, height: 300))
PlaygroundPage.current.liveView = XView()

If you want the fancy version see my GitHub project here: https://github.com/joshuajhomann/pathmorpher/tree/master/final