Check out example codes for "adding label to navigation bar". It will help you in understanding the concepts better.

Code Example 1

if let navigationBar = self.navigationController?.navigationBar {
    let firstFrame = CGRect(x: 0, y: 0, width: navigationBar.frame.width/2, height: navigationBar.frame.height)
    let secondFrame = CGRect(x: navigationBar.frame.width/2, y: 0, width: navigationBar.frame.width/2, height: navigationBar.frame.height)

    let firstLabel = UILabel(frame: firstFrame)
    firstLabel.text = "First"

    let secondLabel = UILabel(frame: secondFrame)
    secondLabel.text = "Second"

    navigationBar.addSubview(firstLabel)
    navigationBar.addSubview(secondLabel)
}

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