create uipresentation contoller in swift

To create a UIPresentationController in Swift, follow the steps below:

1. Create a new class and inherit from UIPresentationController.

main.swift
class MyPresentationController: UIPresentationController {
    // write your code here
}
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2. Implement the required and optional methods of UIPresentationController protocol as per your requirements. Some of the important methods are:

   • presentationTransitionWillBegin(): This method gets called when the presentation animation is about to start. Use this method to set up any views or animations required for the presentation.

   main.swift
    override func presentationTransitionWillBegin() {
        guard let containerView = containerView else { return }
   
        // Add a dimming view behind the presented view controller
        dimmingView.frame = containerView.bounds
        dimmingView.alpha = 0
        containerView.insertSubview(dimmingView, at: 0)
   
        // Animate the dimming view alpha
        if let coordinator = presentingViewController.transitionCoordinator {
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 0.5
            })
        } else {
            dimmingView.alpha = 0.5
        }
    }
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   • dismissalTransitionWillBegin(): This method gets called when the dismissal animation is about to start. Use this method to set up any views or animations required for the dismissal.

   main.swift
   override func dismissalTransitionWillBegin() {
        if let coordinator = presentingViewController.transitionCoordinator {
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 0
            })
        } else {
            dimmingView.alpha = 0
        }
    }
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   • size(forChildContentContainer:withParentContainerSize:): This method is used to provide the size of the presented view controller.

   main.swift
    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerView = containerView,
              let presentedView = presentedView else { return .zero }
   
        let containerViewBounds = containerView.bounds
        let presentedContentSize = size(forChildContentContainer: presentedViewController,
                                         withParentContainerSize: containerViewBounds.size)
        var presentedViewFrame = containerViewBounds
        presentedViewFrame.size.height = presentedContentSize.height
        presentedViewFrame.origin.y = containerViewBounds.maxY - presentedContentSize.height
        presentedView.frame = presentedViewFrame
        return presentedViewFrame
    }
   
    override func size(forChildContentContainer container: UIContentContainer, withParentContainerSize parentSize: CGSize) -> CGSize {
        return CGSize(width: parentSize.width, height: 300)
    }
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3. Use the presentation controller in your presenting view controller.

main.swift
let presentedVC = // instantiate your presented view controller
presentedVC.modalPresentationStyle = .custom
presentedVC.transitioningDelegate = self // the presenting view controller should conform to UIViewControllerTransitioningDelegate
present(presentedVC, animated: true, completion: nil)
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4. Conform to the UIViewControllerTransitioningDelegate protocol in your presenting view controller and implement the following methods:

main.swift
extension MyPresentingViewController: UIViewControllerTransitioningDelegate {
    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        return MyPresentationController(presentedViewController: presented, presenting: presenting)
    }

    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return // create and return an instance of your animated transition class for presentation
    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return // create and return an instance of your animated transition class for dismissal
    }
}
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That's it, you have successfully created a custom UIPresentationController in Swift.