Two-way binding with UIKit

MVVM is a fantastic Architecture pattern for iOS, and is highly recommended to be used in your production code. However, if you do not implement the two-way binding your architecture better represents Model-View-Presenter (MVP).

Many developers will rely on RxSwift and RxCocoa to implement bindings, which is a rather heavyweight solution to simply implement Two-way binding.

This library offers an alternative: provide Two-way bind in a small, tested library.

Installation

This library is intended to be installed as a Swift Package guide, where you would add https://github.com/stevencurtis/SwiftCoding/TwoWayBindingUIKit

Usage

Bind to identical types Values can be created as MakeBindable

var value: MakeBindable<String> = MakeBindable("Test Value")
lazy var label: UILabel = {
    let lab = UILabel()
    return lab
}()

which can then be bound to a UIControl using a keypath: Providing the input and output are the same type (in this case, String is the type for value and the text of label is also a String)

value.bind(\String.self, to: lab, \.text)

Other uses include binding a UIButton and it's isEnabled property, for example:

var buttonEnabled: MakeBindable<Bool> = MakeBindable(true)
buttonEnabled.bind(\Bool.self, to: button, \.isEnabled)

Map bound types If you would like to bind a value to a type that is different to that of the value, you need to provide a mapping function of the type (T) -> R?.

A series of these are provided in this library:

Mappers.transformBoolToStringFunction Mappers.transformFloatToStringFunction Mappers.transformIntToStringFunction

Which are then passed to the bind function. A good example of hte use of this is where we can bind a Boolean value to the text of a UILabel:

var switchValue: MakeBindable<Bool> = MakeBindable(true)
viewModel.switchValue.bind(
    \Bool.self,
    to: switchLabel,
    \.text,
    mapper: Mappers.transformBoolToStringFunction )

If you wish to use a mapper that is not provided, you may also use a mapper inline, and here is an example of how that may be implemented:

let transformBoolToStringFunction: (Bool) -> String = String.init(_:)
viewModel.switchValue.bind(\Bool.self, to: switchLabel, \.text, mapper: transformBoolToStringFunction)

Example Post

There is a full post regarding this library at https://github.com/stevencurtis/SwiftCoding/TwoWayBinding