extension for constraints for applying programmatically in swift 5.1

ConstraintsExtesnions.swift

extension UIView {
    func addSubviewsUsingAutoLayout(_ views: UIView ...) {
        subviews.forEach {
            self.addSubview($0)
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
    }
}

@objc extension NSLayoutAnchor {
    @discardableResult
    func constrain(_ relation: NSLayoutConstraint.Relation = .equal,
                   to anchor: NSLayoutAnchor,
                   with constant: CGFloat = 0.0,
                   prioritizeAs priority: UILayoutPriority = .required,
                   isActive: Bool = true) -> NSLayoutConstraint {
        var constraint: NSLayoutConstraint
        switch relation {
            case .equal:
                constraint = self.constraint(equalTo: anchor, constant: constant)
            case .greaterThanOrEqual:
                constraint = self.constraint(greaterThanOrEqualTo: anchor, constant: constant)
            case .lessThanOrEqual:
                constraint = self.constraint(lessThanOrEqualTo: anchor, constant: constant)
            @unknown default:
                fatalError()
        }
        constraint.set(priority: priority, isActive: isActive)
        return constraint
    }
}


extension NSLayoutDimension {
    
    @discardableResult
    func constrain(_ relation: NSLayoutConstraint.Relation = .equal,
                   to anchor: NSLayoutDimension,
                   with constant: CGFloat = 0.0,
                   multiplyBy multiplier: CGFloat = 1.0,
                   prioritizeAs priority: UILayoutPriority = .required,
                   isActive: Bool = true) -> NSLayoutConstraint {
        let constraint: NSLayoutConstraint
        switch relation {
            case .equal:
                constraint = self.constraint(equalTo: anchor, multiplier: multiplier, constant: constant)
            case .greaterThanOrEqual:
                constraint = self.constraint(greaterThanOrEqualTo: anchor, multiplier: multiplier, constant: constant)
            case .lessThanOrEqual:
                constraint = self.constraint(lessThanOrEqualTo: anchor, multiplier: multiplier, constant: constant)
            @unknown default:
                fatalError()
        }
        constraint.set(priority: priority, isActive: isActive)
        return constraint
    }
    
    @discardableResult
    func constrain(_ relation: NSLayoutConstraint.Relation = .equal,
                   to constant: CGFloat = 0.0,
                   prioritizeAs priority: UILayoutPriority = .required,
                   isActive: Bool = true) -> NSLayoutConstraint {
        var constraint: NSLayoutConstraint
        switch relation {
            case .equal:
                constraint = self.constraint(equalToConstant: constant)
            case .greaterThanOrEqual:
                constraint = self.constraint(greaterThanOrEqualToConstant: constant)
            case .lessThanOrEqual:
                constraint = self.constraint(lessThanOrEqualToConstant: constant)
            @unknown default:
                fatalError()
        }
        constraint.set(priority: priority, isActive: isActive)
        return constraint
    }
}
extension UILayoutPriority {
    static func +(lhs: UILayoutPriority, rhs: Float) -> UILayoutPriority {
        return UILayoutPriority(lhs.rawValue + rhs)
    }
    static func -(lhs: UILayoutPriority, rhs: Float) -> UILayoutPriority {
        return UILayoutPriority(lhs.rawValue - rhs)
    }
}
extension NSLayoutConstraint {
    func set(priority: UILayoutPriority, isActive: Bool) {
        self.priority = priority
        self.isActive = isActive
    }
}

/////////////////////Usage/////////////////////
// Subviews
let logoImageView = UIImageView()
let welcomeLabel = UILabel()
let dismissButton = UIButton()
        
// Add Subviews & Set view's translatesAutoresizingMaskIntoConstraints to false
addSubviewsUsingAutoLayout(logoImageView, welcomeLabel, dismissButton)
        
// Set Constraints
logoImageView.topAnchor.constrain(to: topAnchor, with: 12)
logoImageView.centerXAnchor.constrain(to: centerXAnchor)
logoImageView.widthAnchor.constrain(to: 50)
logoImageView.heightAnchor.constrain(to: 50)
        
dismissButton.leadingAnchor.constrain(.greaterThanOrEqual, to: leadingAnchor, with: 12)
dismissButton.trailingAnchor.constrain(.lessThanOrEqual, to: trailingAnchor, with: -12)
dismissButton.bottomAnchor.constrain(to: bottomAnchor)
dismissButton.widthAnchor.constrain(to: 320, prioritizeAs: .defaultHigh + 1)
        
welcomeLabel.topAnchor.constrain(to: logoImageView.bottomAnchor, with: 12)
welcomeLabel.bottomAnchor.constrain(.greaterThanOrEqual, to: dismissButton.topAnchor, with: 12)
welcomeLabel.leadingAnchor.constrain(to: dismissButton.leadingAnchor)
welcomeLabel.trailingAnchor.constrain(to: dismissButton.trailingAnchor)


//Credit goes to https://pedrommcarrasco.github.io/posts/power-up-your-anchors/