carabina / segueperformer

A Swift class for initiating segues programatically, using closures for view controller preparation

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
        }
    }

}