Swapper

Swap between many different UIViews within your app quick and easy.

Android developer? Check out the Android version of Swapper!

What is Swapper?

You know those moments in your app when you have a UITableView that has no rows to show? You know those moments when you perform a HTTP network request and you want to show a non-blocking loading view to the user? These are very common scenarios for mobile apps. Swapper is a UIView that allows you to swap between a set of other UIViews with just 1 line of code.

Why use Swapper?

• Swift API
• Lightweight. Zero dependencies.
• UI testing friendly.
• Setup with default values that should work for 95% of your use cases. Customizable for those other cases.
• Full test suite.
• Full documentation.

I recommend you check out 2 other libraries that work nicely with Swapper: Empty and PleaseHold.

Installation

Swapper is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'Swapper', '~> version-here'

Replace version-here with: as this is the latest version at this time.

Getting started

• Create an instance of SwapperView in your UIViewController. You can do this with Storyboard by adding a UIView to Storyboard and setting the UIView class to SwapperView, or create an instance in your Swift code:

let swapperView: SwapperView<ViewControllerSwapViews> = {
    let view = SwapperView<ViewControllerSwapViews>()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = .white
    return view
}()

• Make sure to create the UIViews that you want to swap between. In this example, let’s assume that I created a UITableView and a UIImageView that I want to swap between.

In your UIViewController, add your UIViews to your SwapperView:

import Swapper

// It's recommended to use emum for the identifier. It will prevent bugs by not worrying about typos. 
// However, you can just as easily use `SwapperView<String>` or something similar. 
enum ViewControllerSwapViews: String, CustomStringConvertible {
    case imageView
    case tableView

    var description: String {
        return rawValue
    }
}

class ViewController: UIViewController {

    let swapperView = SwapperView<ViewControllerSwapViews>()

    override func viewDidLoad() {
        super.viewDidLoad()

        // `setSwappingViews` will remove all subviews from the SwapperView. Reset it. 
        swapperView.setSwappingViews([
            (.imageView, myImageView),
            (.tableView, myTableView)
        ], swapTo: .imageView) // `swapTo` is optional and is used to swap to one of the views after setting new swapping views. 
    }

}

Note: Swapper holds onto UIView instances given with setSwappingViews() as a weak reference. Keep your own strong reference to make sure the app is working.

Note: Swapper will update the AutoLayout constraints of the UIViews you set as the swapping views. Swapper will set the size as the same size you set as the SwapperView. Therefore, no need to set AutoLayout constraints on your own! If you’re not using AutoLayout, edit the configuration for SwapperView to not update the constraints: SwapperView.defaultConfig.updateAutoLayoutConstraints = false.

• Lastly, all you need to do is to tell Swapper to swap!

try! swapperView.swapTo(.tableView)

Swapper will now show the UITableView for you. Swapper will even fade out the UIImageView and fade in the UITbleView for you for a nice touch 👌. If you want to override the default animation, you can override the behavior yourself:

SwapperView.defaultConfig.swapToAnimateOldView = { oldView in
    // Run `UIView.animate()` function here on `oldView` to animate it out. 
}
SwapperView.defaultConfig.swapToAnimateNewView = { newView in
    // Run `UIView.animate()` function here on `newView` to animate it in. 
}

Note: .swapTo() will thrown an error if the id passed in was not given in .setSwappingViews(). Or, the view you passed in has been garbage collected. Swapper only keeps weak references to given UIViews.

Configure Swapper

Swapper works great without any configuration necessary. However, if you wish to customize it yourself, you can.

If you want to change the default values of all instances of SwapperView in your app, change the values in the default singleton:

SwapperView.defaultConfig.transitionAnimationDuration = 0.8

Or, you can configure 1 single instance of SwapperView:

let swapperView = SwapperView()
var instanceConfig: SwapperViewConfig {
    let config = SwapperViewConfig()
    config.backgroundColor = instanceConfigBackgroundColor
    return config
}
swapperView.config = instanceConfig

For a list of all the configuration options, view the docs on SwapperViewConfig

Testing with Swapper

If you want to write tests for your app and include Swapper in it, it’s highly recommended to disable animations.

UIView.setAnimationsEnabled(false)

Done! Swapper inherits this property and will enable or disable animations with this setting.

Example

Swapper comes with an example app you can use to play with the library. To run the example project, clone the repo, and run pod install from the Example directory first. Then, open the workspace in XCode.

Development

Swapper is a pretty simple CocoaPods library project. Follow the directions below for the optimal development experience.

• Install cocoapods/gems and setup workspace:

$> bundle install
$> cd Swapper/Example
$> pod install
$> brew install swiftformat
$> brew install swiftlint

• Setup git hooks to run misc tasks for you when using git.

$> brew install pre-commit
$> ./hooks/autohook.sh install

The git hook scripts are installed in hooks/. View them if you wish.

Contributors ✨

Thanks goes to these wonderful people (emoji key):

Contribute

Swapper is open for pull requests. Check out the list of issues for tasks I am planning on working on. Check them out if you wish to contribute in that way.

Want to add features to Swapper? Before you decide to take a bunch of time and add functionality to the library, please, create an issue stating what you wish to add. This might save you some time in case your purpose does not fit well in the use cases of Swapper.

License

Swapper is available under the MIT license. See the LICENSE file for more info.