This library is used with RxSwift to provide an abstraction on top of observables: actions.

An action is a way to say "hey, later I'll need you to subscribe to this thing." It's actually a lot more involved than that.

Actions accept a workFactory: a closure that takes some input and produces an observable. When execute() is called on the action, the workFactory gets passed this parameter and the action subscribes to the observable that gets returned.

An action:

• Can only be executed while "enabled" (true if unspecified).
• Only executes one thing at a time.
• Aggregates next/error events across individual executions.

Oh, and it has this really Swift thing with UIButton that's pretty cool. It'll manage the button's enabled state, make sure the button is disabled while your work is being done, all that stuff 👍

You have to pass a workFactory that takes input and returns an Observable. This represents some work that needs to be accomplished. Whenever you call execute(), you pass in input that's fed to the work factory. The Action will subscribe to the observable and emit the Next events on its elements property. If the observable errors, the error is sent as a Next even on the errors property. Neat.

Actions can only execute one thing at a time. If you try to execute an action that's currently executing, you'll get an error. The executing property sends true and false values as Next events.

action: Action<String, Bool> = Action(workFactory: { input in
    return networkLibrary.checkEmailExists(input)
})

...

action.execute("[email protected]")

Notice that the first generic parameter is the type of the input, and the second is the type of observable that workFactory creates. You can think of it a bit like the action's "output."

You can also specify an enabledIf parameter to the Action initializer.

let validEmailAddress = emailTextField.rx.text.map(isValidEmail)

action: Action<String, Bool> = Action(enabledIf: validEmailAddress, workFactory: { input in
    return networkLibrary.checkEmailExists(input)
})

Now execute() only does the work if the email address is valid. Super cool!

(Note that enabledIf isn't the same as the enabled property. You pass in enabledIf and the action uses that (combined with its current executing state) to determine if it's currently enabled.)

What's really cool is the UIButton extension. It accepts a CocoaAction, which is just Action<Void, Void>.

button.rx.action = action

Now when the button is pressed, the action is executed. The button's enabled state is bound to the action's enabled property. That means you can feed your form-validation logic into the action as a signal, and your button's enabled state is handled for you. Also, the user can't press the button again before the action is done executing, since it only handles one thing at a time. Cool. Check out this code example of CocoaAction in action.

If you'd like to use Action to do a complex operation such as file download with download progress report (to update progress bar in the UI for example) you'd use Action<Void, Int> instead of CocoaAction. Out of the box CocoaAction can't emit progress values, your own Action<Void, Int> will do that. For details refer to this article.

If your scenario involves many buttons that needs to trigger the same Action providing different input, you can use bindTo on each UIButton with a closure that returns correct input.

let button1 = UIButton()
let button2 = UIButton()

let action = Action<String, String> { input in
    print(input)
    return .just(input)
}
button1.rx.bindTo(action) { _ in return "Hello"}
button2.rx.bindTo(action) { _ in return "Goodbye"}

button1 and button2 are sharing the same Action, but they are feeding it with different input (Hello and Goodbye that will be printed for corresponding tap).

A more complex use case can be a single action related to a UIViewController that manages your navigation, error handling and loading state. With this approach, you can have as many UIButtons (or UIBarButtonItems) as you want and subscribe to executing, errors, elements and completions once and in a single common place.

There's also a really cool extension on UIAlertAction, used by UIAlertController. One catch: because of the limitations of that class, you can't instantiate it with the normal initializer. Instead, call this class method:

let action = UIAlertAction.Action("Hi", style: .default)

Just add the line below to your Podfile:

pod 'Action'

Then run pod install and that'll be 👌

Add this to Cartfile

github "RxSwiftCommunity/Action" ~> 5.0.0

If you are using RxSwift 3.2.0 or below, Use Action ~2.2.0 instead!

then run

> carthage update

This library is (pretty obviously) inspired by ReactiveCocoa's Action class. Those developers deserve a lot of thanks!

MIT obvs.