Reactive

A small Swift Package for data binding.

Installation

Method 1: Swift Package Manager

1. In Xcode, go to File > Swift Packages > Add Package Dependency.
2. Enter https://github.com/chhaylatte/Reactive/ for the repository URL.
3. Select the desired version and press Next.

Method 2: Carthage

1. Add github "chhaylatte/Reactive" in the Cartfile.
2. Open Carthage/Build and locate the relevant Reactive.framework for the desired platform.
3. Drag the Reactive.framework bundle into the Frameworks, Libraries, and Embedded Content section of the Project Target in Xcode.

What

Reactive is a wrapper object that implements an observer system to notify listeners of initial and updated values. There is no stream of data, just single update propagation.

Why

Reactive style can help keep code maintainable by reducing the amount of code and complexity. Team or project constraints, such as requiring older versions of iOS, may not allow the use of a reactive framework such as Combine or RxSwift, so Reactive can be an alternative. Reactive works with Swift 5.1, and takes very little time to learn. Reactive does not need any extra coding overhead of unsubscribing, retaining, or releasing any objects. Reactive is smart enough to discard handlers if the associated listener is deallocated.

How

Reactive is conceptually just a wrapper object that provides a built in observer method. Simply use the bind method on Reactive to define how to handle new and initial values. Reactive can be used as either a wrapper object, or as a Swift property wrapper.

Reactive Object

Initialize a Reactive wrapper with any type that is intended to be observed. For example, a String value that is needed to set the text of a label.

class MyClass {
    let title = Reactive("Title")   // `title` is implicitly of type `Reactive<String>` in this case
}
let myClass = MyClass()
print(myClass.title.wrappedValue)      // Prints "Title"

To start listening, call the bind(_ listener:, skipInitialValue:, handler:) method. The handler is called after every update call on the Reactive object.

let titleLabel = UILabel()
myClass.title.bind(titleLabel) { (aLabel, string) in // This handler will be called with the listener and new/initial values as parameters
    alabel.text = string    // Update the text of the listener.
}

To change the value call the update(_ value:) method.

myClass.title.update("New Title")   // The handler is now triggered, updating the text of the label

To stop listening for values, call the unbind(_ listener:) method.

myClass.title.unbind(titleLabel)    // All handlers associated to `titleLabel` are now removed

Reactive Property Wrapper

The @Reactive property wrapper offers syntactic sugar. Internally, it is the same as the Reactive object

class MyClass {
    @Reactive var title: String = ""
}

let myClass = MyClass()
print(myClass.title)        // prints ""

myClass.title = "New Title" // Updates the title
print(myClass.title)        // prints "New Title"

To bind or unbind a reactive property, use its property projection.

let titleLabel = UILabel()
myClass.$title.bind(titleLabel) { (aLabel, string) in   // This handler will be called with the listener and new/initial values as parameters
    aLabel.text = string
}
myClass.title = "Newest Title"  // titleLabel's text is now updated to "Newest Title"

myClass.$title.unbind(titleLabel)    // All handlers associated to `titleLabel` are removed