SeguePerformer

Purpose

The SeguePerformer class provides an interface for initiating UIKit segues programatically, using closures for view controller preparation.

In UIKit's existing programmatic segue presentation interface, UIViewController's performSegue(withIdentifier:sender:) method relies on a non-local definition of prepare(for:sender:) to configure the new view controller before it is presented. This can become unweildy in the context of multiple performSegue calls.

SeguePerformer improves upon this by providing a performSegue(withIdentifier:sender:preparationHandler:) method which allows for configuration of the new view controller via a trailing closure parameter.

Installation

To install SeguePerformer using CocoaPods, add the following to your Podfile:

pod 'SeguePerformer'

Or, if you prefer, drag SeguePerformer.swift into your project.

Usage

1. Add a lazy seguePerformer property to your view controller.
2. Call seguePerformer.performSegue(withIdentifier:sender:preparationHandler:) to initiate segues whose destination view controllers require configuration.
3. Override your view controller's prepare(for:sender:) method, passing its parameters along to seguePerformer.prepare(for:sender:). Without this step, the preparationHandler closure will never be called.

Example

import SeguePerformer

class MyPresentingViewController: UIViewController {

    lazy var seguePerformer = SeguePerformer(viewController: self)

    func performMySegue(with myPropertyValue: Int) {
        // Perform the segue, configuring the destination view controller
        // before it is presented.
        seguePerformer.performSegue(withIdentifier: "mySegue", sender: self) {
            (myPresentedViewController: MyPresentedViewController) in
            myPresentedViewController.myProperty = myPropertyValue
        }
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // For SeguePerformer.performSegue's trailing closure to be called,
        // SeguePerformer must be notified about the prepare(for:sender:) call.
        if seguePerformer.prepare(for: segue, sender: sender) {
            return
        }

        // Prepare for interactive segues configured in Storyboard here.
    }

}

Without SeguePerformer, the traditional way of writing this would be:

class MyPresentingViewController: UIViewController {

    var myPresentedViewControllerPropertyValue: Int?

    func performMySegue(with myPropertyValue: Int) {
        myPresentedViewControllerPropertyValue = myPropertyValue
        performSegue(withIdentifier: "mySegue", sender: self)
        // Continues in prepare(for:sender:)...
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let myPresentedViewController = segue.destination as? MyPresentedViewController,
            let myPresentedViewControllerPropertyValue = myPresentedViewControllerPropertyValue {
            // ...continued from performMySegue(with:)
            myPresentedViewController.myProperty = myPresentedViewControllerPropertyValue
            self.myPresentedViewControllerPropertyValue = nil
        }
    }

}