How to create UILabel programmatically using Swift?

Question

Creating a UILabel programmatically in Swift 3+:

override func viewDidLoad() {
    super.viewDidLoad()

    let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 21))
    label.center = CGPoint(x: 160, y: 285)
    label.textAlignment = .center
    label.text = "I'm a test label"

    self.view.addSubview(label)
}

Here is the correct code for Swift 3, with comments for instructional purposes:

override func viewDidLoad()
{
    super.viewDidLoad()

    // CGRectMake has been deprecated - and should be let, not var
    let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 21))

    // you will probably want to set the font (remember to use Dynamic Type!)
    label.font = UIFont.preferredFont(forTextStyle: .footnote)

    // and set the text color too - remember good contrast
    label.textColor = .black

    // may not be necessary (e.g., if the width & height match the superview)
    // if you do need to center, CGPointMake has been deprecated, so use this
    label.center = CGPoint(x: 160, y: 284)

    // this changed in Swift 3 (much better, no?)
    label.textAlignment = .center

    label.text = "I am a test label"

    self.view.addSubview(label)
}

Just to add onto the already great answers, you might want to add multiple labels in your project so doing all of this (setting size, style etc) will be a pain. To solve this, you can create a separate UILabel class.

  import UIKit

  class MyLabel: UILabel {

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initializeLabel()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        initializeLabel()
    }

    func initializeLabel() {

        self.textAlignment = .left
        self.font = UIFont(name: "Halvetica", size: 17)
        self.textColor = UIColor.white

    }

}

To use it, do the following

import UIKit

class ViewController: UIViewController {

     var myLabel: MyLabel()

     override func viewDidLoad() {
          super.viewDidLoad()

          myLabel = MyLabel(frame: CGRect(x: self.view.frame.size.width / 2, y: self.view.frame.size.height / 2, width: 100, height: 20))
          self.view.addSubView(myLabel)
     }


}

Swift 4.X and Xcode 10

let lbl = UILabel(frame: CGRect(x: 10, y: 50, width: 230, height: 21))
lbl.textAlignment = .center //For center alignment
lbl.text = "This is my label fdsjhfg sjdg dfgdfgdfjgdjfhg jdfjgdfgdf end..."
lbl.textColor = .white
lbl.backgroundColor = .lightGray//If required
lbl.font = UIFont.systemFont(ofSize: 17)

//To display multiple lines in label
lbl.numberOfLines = 0 //If you want to display only 2 lines replace 0(Zero) with 2.
lbl.lineBreakMode = .byWordWrapping //Word Wrap
// OR
lbl.lineBreakMode = .byCharWrapping //Charactor Wrap

lbl.sizeToFit()//If required
yourView.addSubview(lbl)

If you have multiple labels in your class use extension to add properties.

//Label 1
let lbl1 = UILabel(frame: CGRect(x: 10, y: 50, width: 230, height: 21))
lbl1.text = "This is my label fdsjhfg sjdg dfgdfgdfjgdjfhg jdfjgdfgdf end..."
lbl1.myLabel()//Call this function from extension to all your labels
view.addSubview(lbl1)

//Label 2
let lbl2 = UILabel(frame: CGRect(x: 10, y: 150, width: 230, height: 21))
lbl2.text = "This is my label fdsjhfg sjdg dfgdfgdfjgdjfhg jdfjgdfgdf end..."
lbl2.myLabel()//Call this function from extension to all your labels
view.addSubview(lbl2)

extension UILabel {
    func myLabel() {
        textAlignment = .center
        textColor = .white
        backgroundColor = .lightGray
        font = UIFont.systemFont(ofSize: 17)
        numberOfLines = 0
        lineBreakMode = .byCharWrapping
        sizeToFit()
    }
}