How can I get array of UIStoryboard in Swift?

Question

I find that my Storyboard has become very complex and decided to split it into different Storyboards. But I want to have the freedom to instantiate a UIViewController no matter where I put the view controller in. That way, I can move around View Controller from Storyboard to Storyboard without the need to remember where did I put that View Controller, and I also don't have to update the code at all because they all use the same code to instantiate the same View Controller with that name, no matter where it resides.

Therefore, I want to create an extension of UIViewController like this:

extension UIViewController {

    func instantiate (named: String?, fromStoryboard: String? = nil) -> UIViewController? {
    guard let named = named else { return nil; }
    if let sbName = fromStoryboard {
        let sb = UIStoryboard(name: sbName, bundle: nil);
        return sb.instantiateViewController(withIdentifier: named);
    }
    else {
        for sb in UIStoryboard.storyboards {
            if let vc = sb.instantiateViewController(withIdentifier: named) {
                return vc;
            }
        }
    }
    return nil;
}

The problem is, I cannot find the property / method to return the list of storyboard instances like .storyboards anywhere. Is there any workaround on this? I know that I can probably have a static list of storyboard names, but that way, the extension won't be dynamic and independent of the projects.

Can anybody help? Thanks.

EDIT:

Combining the accepted answer and answer from here to safely instantiate viewcontroller (and return nil if not found), this is my code:

UIStoryboard+Storyboards.swift:

extension UIStoryboard {

    static var storyboards : [UIStoryboard] {
        let directory = Bundle.main.resourcePath! + "/Base.lproj"
        let allResources = try! FileManager.default.contentsOfDirectory(atPath: directory)
        let storyboardFileNames = allResources.filter({ $0.hasSuffix(".storyboardc" )})
        let storyboardNames = storyboardFileNames.map({ ($0 as NSString).deletingPathExtension as String })
        let storyboardArray = storyboardNames.map({ UIStoryboard(name: $0, bundle: Bundle.main )})
        return storyboardArray;
    }

    func instantiateViewControllerSafe(withIdentifier identifier: String) -> UIViewController? {
        if let availableIdentifiers = self.value(forKey: "identifierToNibNameMap") as? [String: Any] {
            if availableIdentifiers[identifier] != nil {
                return self.instantiateViewController(withIdentifier: identifier)
            }
        }
        return nil
    }

}

UIViewController+Instantiate.swift:

extension UIViewController {

    static func instantiate (named: String?, fromStoryboard: String? = nil) -> UIViewController? {
        guard let named = named else { return nil; }
        if let sbName = fromStoryboard {
            let sb = UIStoryboard(name: sbName, bundle: nil);
            return sb.instantiateViewControllerSafe(withIdentifier: named);
        }
        else {
            for sb in UIStoryboard.storyboards {
                if let vc = sb.instantiateViewControllerSafe(withIdentifier: named) {
                    return vc;
                }
            }
        }
        return nil;
    }
}

With the restriction that all the storyboard files must be located on Base.lproj folder.

It's not the most efficient code in terms of running time, I know. But for now, it's easy enough to be understood and I can live with this. :) Thanks for everybody who helps!

user_2431627 · Answer

As stated elsewhere storyboards are compiled to opaque (i.e. binary, undocumented) .storyboardc files when the app is compiled and run. The UIStoryboard API only allows instantiating the initial View Controller, or a (known) named one, so there's no naive way to interrogate your app for 'unknown' storyboard elements. There may also be side-effects to instantiating UI elements that are not being displayed. However...

If you put your .storyboard files in a Copy Files build phase you can interrogate the XML and recover e.g. UIViewController/UIView identifiers, custom properties etc. IBDecodable seems to do a reasonable job of this. Installation-wise (cocoapods) it's MacOS-only but will run happily if you embed it in your iOS app (install the SWXMLHash prerequisite and clone IBDecodable/git-submodule it, whatever). There are probably efficiency and localisation issues I'm skimping on but for my use case (building onboarding popovers from custom properties without being explicit about it) it worked OK.

To answer the question posed more specifically, interrogating the storyboards for IDs would allow the app to find (via a dict or similar), and instantiate a View Controller, wherever it was visually stored.

For example:

Bundle.main.urls(forResourcesWithExtension: "storyboard", subdirectory: nil)?
    .forEach({ (url) in
        do {
            let file = try StoryboardFile(url: url)
            if !file.document.launchScreen {
                file.document.scenes?.forEach({ (scene) in
                    scene.viewController?.viewController.rootView?.subviews?
                        .forEach({ (view) in
                            // Do stuff...
                        })
                    })
                }
            } catch { /* ... */ }
        })

How can I get array of UIStoryboard in Swift?

4 Answers