如何在同一容器 Swift 内的 nib 视图之间切换？

Question

I have a container with a few reusable elements: imageView, label and a stackView.

class ContainerViewController: UIViewController {

// MARK: - Constants

var stepList = [UIViewController]()

// MARK: - Outlets
@IBOutlet private(set) weak var logoImageview: UIImageView!
@IBOutlet private(set) weak var titleLabel: UILabel!
@IBOutlet private(set) weak var progressStackView: UIStackView!

. . .
}

I also have another three viewControllers designed with Nib files, let's call them oneVC, twoVC and threeVC. This is how they look:

class StepOneViewController: UIViewController {

// MARK: - Constants
. . .

@IBOutlet private(set) weak var nextButton: UIButton!

. . .
}

Each controller has it's own nextButton, and it's own IBAction to trigger when that button is tapped. It should make a push to the next viewController, but that's not happening.

When you access the container, the oneVC is displayed among the reusable elements of the container. This works.

I don't know how to access each button of my controllers from my containerController. I need to achieve that to show the next nib, and it must be able to go back too.

This code from my ContainerViewController add each controller's view as a subview:

private func setupControllers() {
    stepList.append(StepOneViewController(nibName: "StepOneViewController", bundle: nil))
    stepList.append(StepTwoViewController(nibName: "StepTwoViewController", bundle: nil))
    stepList.append(StepThreeViewController(nibName: "StepThreeViewController", bundle: nil))

    guard let stepOneView   = stepList.first?.view,
          let stepTwoView   = stepList[1].view,
          let stepThreeView = stepList.last?.view
    else { return }
    
    configureStepViewsLayout(onStepView: stepOneView)
    
    
}

private func configureStepViewsLayout(onStepView stepView: UIView) {
    view.addSubview(stepView)
    stepView.translatesAutoresizingMaskIntoConstraints = false
    let guide = view.safeAreaLayoutGuide
    NSLayoutConstraint.activate([
        stepView.topAnchor.constraint(equalTo: progressStackView.bottomAnchor,
                                         constant: 20),
        stepView.leftAnchor.constraint(equalTo: guide.leftAnchor),
        stepView.rightAnchor.constraint(equalTo: guide.rightAnchor),
        stepView.bottomAnchor.constraint(equalTo: guide.bottomAnchor)
    ])
}

I also need to change the progressStackView color every time any nextButton is tapped and shows the next controller.

Answer 1

What you're doing is totally illegal. You cannot simply say

view.addSubview(stepView)

out of the blue like that. You are effectively just using the nib as a form of dumpster diving; you are grabbing the view and shoving it into your interface, but the view controller (eg StepOneViewController) bears no formal relationship to your view controller (ContainerViewController). You are using the word "container", but this is not a container view controller.

There is an elaborate parent–child dance that you must do in order to get the child (eg StepOneViewController) into the view controller hierarchy and make your container view controller be a container view controller — and you are not doing the dance.

Once you do the dance, the child will be able to talk to the parent as its parent . The parent can then remove the child (again using a formal dance) and replace it with another.

Also, it's a really bad idea to retain three view controllers as you are doing. You only have one visible child view at a time so you only need one child view controller at any given moment.