How to make a custom reusable view in iOS

CreateCustomReusableView.swift

import Foundation
import UIKit

class CustomView: UIView {
    
    convenience init() {
        // Size doesn't matter if your widget is scalable
        // and you are going to use Autolayout constraints
        // on it
        self.init(frame: CGRectZero)
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.setupHierarchy()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.setupHierarchy()
    }
    
    func setupHierarchy() {
        // Do your setup here (set properties, add subviews, etc.)
    }
    
    // ...
    
}