Toast notification class for swift 4 like android

Toast.swift

import Foundation
import UIKit

public extension UIView {
    
    public func showToast(message:String, duration:Int = 2000) {
        
        let toastLabel = UIPaddingLabel();
        toastLabel.padding = 10;
        toastLabel.translatesAutoresizingMaskIntoConstraints = false;
        toastLabel.backgroundColor = UIColor.darkGray;
        toastLabel.textColor = UIColor.white;
        toastLabel.textAlignment = .center;
        toastLabel.text = message;
        toastLabel.numberOfLines = 0;
        toastLabel.alpha = 0.9;
        toastLabel.layer.cornerRadius = 20;
        toastLabel.clipsToBounds = true;
        
        self.addSubview(toastLabel);
        
        self.addConstraint(NSLayoutConstraint(item:toastLabel, attribute:.left, relatedBy:.greaterThanOrEqual, toItem:self, attribute:.left, multiplier:1, constant:20));
        self.addConstraint(NSLayoutConstraint(item:toastLabel, attribute:.right, relatedBy:.lessThanOrEqual, toItem:self, attribute:.right, multiplier:1, constant:-20));
        self.addConstraint(NSLayoutConstraint(item:toastLabel, attribute:.bottom, relatedBy:.equal, toItem:self, attribute:.bottom, multiplier:1, constant:-20));
        self.addConstraint(NSLayoutConstraint(item:toastLabel, attribute:.centerX, relatedBy:.equal, toItem:self, attribute:.centerX, multiplier:1, constant:0));
        
        UIView.animate(withDuration:0.5, delay:Double(duration) / 1000.0, options:[], animations: {
            
            toastLabel.alpha = 0.0;
            
        }) { (Bool) in
            
            toastLabel.removeFromSuperview();
        }
    }
}

@IBDesignable class UIPaddingLabel: UILabel {
    
    private var _padding:CGFloat = 0.0;
    
    public var padding:CGFloat {
        
        get { return _padding; }
        set {
            _padding = newValue;
            
            paddingTop = _padding;
            paddingLeft = _padding;
            paddingBottom = _padding;
            paddingRight = _padding;
        }
    }
    
    @IBInspectable var paddingTop:CGFloat = 0.0;
    @IBInspectable var paddingLeft:CGFloat = 0.0;
    @IBInspectable var paddingBottom:CGFloat = 0.0;
    @IBInspectable var paddingRight:CGFloat = 0.0;
    
    override func drawText(in rect: CGRect) {
        let insets = UIEdgeInsets(top:paddingTop, left:paddingLeft, bottom:paddingBottom, right:paddingRight);
        super.drawText(in: UIEdgeInsetsInsetRect(rect, insets));
    }
    
    override var intrinsicContentSize: CGSize {
        
        get {
            var intrinsicSuperViewContentSize = super.intrinsicContentSize;
            intrinsicSuperViewContentSize.height += paddingTop + paddingBottom;
            intrinsicSuperViewContentSize.width += paddingLeft + paddingRight;
            return intrinsicSuperViewContentSize;
        }
    }
}