Sample of NSLayoutConstraint

ViewController.swift

label.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(label)
view.addConstraints([
    NSLayoutConstraint(
        item: label,
        attribute: .width,
        relatedBy: .equal,
        toItem: nil,
        attribute: .width,
        multiplier: 1.0,
        constant: 100
    ),
    NSLayoutConstraint(
        item: label,
        attribute: .height,
        relatedBy: .equal,
        toItem: nil,
        attribute: .height,
        multiplier: 1.0,
        constant: 100
    ),
    NSLayoutConstraint(
        item: label,
        attribute: .centerX,
        relatedBy: .equal,
        toItem: view,
        attribute: .centerX,
        multiplier: 1.0,
        constant: 0.0
    ),
    NSLayoutConstraint(
        item: label,
        attribute: .centerY,
        relatedBy: .equal,
        toItem: view,
        attribute: .centerY,
        multiplier: 1.0,
        constant: 0.0
    ),
])