arrays - declare var as a group in swift

Question

I want to declare a group of the same objects like this.

var dave, paul, sam = UILabel()

I have tried various things. But I have not been able to do anything different to declare vars except the standard.

var dave = UILabel()
var paul = UILabel()
var sam = UILabel()

I would think there has to be someway to put this in a array to speed up the process.

标签： arraysswiftinitializationdeclarationvar

Answer 1

Rather than using named variables, you can just create an array of labels:

let labels = (0..<3).map { _ in UILabel() }

Or you might as well configure them as you create them:

let labels = (0..<3).map { _ -> UILabel in 
    let label = UILabel()
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}

You can do whatever other configuration of them you want in that closure.

Now you can use them. For example, you might add them to your view which already has a vertical stack view (which gets you out of the business of manually adding constraints for each label), like so:

func viewDidLoad() {
    super.viewDidLoad()

    for label in labels {
        stackView.addArrangedSubview(label)
    }
}

And if you wanted to set the text for these labels:

labels[0].text = "Dave"
labels[1].text = "Paul"
labels[2].text = "Sam"

---

Here is a playground that illustrates the above:

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {
    let stackView: UIStackView = {
        let stackView = UIStackView()
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        return stackView
    }()

    let labels = (0..<3).map { _ -> UILabel in 
        let label = UILabel()
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        addStackView()
        addLabels()
        updateLabels()
    }
}

private extension ViewController {
    func addStackView() {
        view.addSubview(stackView)
        NSLayoutConstraint.activate([
            stackView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        ])
    }

    func addLabels() {
        for label in labels {
            stackView.addArrangedSubview(label)
        }
    }

    func updateLabels() {
        labels[0].text = "Dave"
        labels[1].text = "Paul"
        labels[2].text = "Sam"
    }
}

PlaygroundPage.current.liveView = ViewController()

Now, if this was a proper app rather than a playground, I’d probably just add the stack view in IB, with an @IBOutlet, rather than doing it programmatically, but I just wanted to illustrate the idea.