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View Transition mechanism for MVVM pattern (Swift, iOS)
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import UIKit | |
// MARK: - Specification | |
protocol ViewType { | |
associatedtype ViewModel: ViewModelType | |
var viewModel: ViewModel { get } | |
//init(viewModel: ViewModel) // Not possible for storyboard-based view controllers. | |
static func instantiate(viewModel viewModel: ViewModel) -> Self | |
} | |
protocol ViewModelType { | |
associatedtype Model | |
var model: Model { get } | |
init(model: Model) | |
} | |
protocol ViewFactoryType { | |
associatedtype View: ViewType | |
func createView(model model: View.ViewModel.Model) -> View | |
} | |
protocol ModelTransformationType { | |
associatedtype SrcModel | |
associatedtype DstModel | |
func transform(m: SrcModel) -> DstModel | |
} | |
protocol ViewPresentationType { | |
associatedtype SrcView: ViewType | |
associatedtype DstView: ViewType | |
func present(srcView srcView: SrcView, dstView: DstView) | |
} | |
protocol ViewTransitionType { | |
associatedtype SrcView: ViewType | |
func performTransition(srcView srcView: SrcView) | |
} | |
// MARK: - Implementation | |
final class ModelTransformation<SrcModel, DstModel>: ModelTransformationType { | |
private let body: SrcModel -> DstModel | |
init(body: SrcModel -> DstModel) { | |
self.body = body | |
} | |
func transform(m: SrcModel) -> DstModel { | |
return body(m) | |
} | |
} | |
final class PushPresentation<SrcView: ViewType, DstView: ViewType | |
where SrcView: UIViewController, DstView: UIViewController>: ViewPresentationType | |
{ | |
private let animated: Bool | |
init(animated: Bool) { | |
self.animated = animated | |
} | |
func present(srcView srcView: SrcView, dstView: DstView) { | |
srcView.navigationController?.pushViewController(dstView, animated: animated) | |
} | |
} | |
final class ViewTransition<ModelTransformation: ModelTransformationType, DstViewFactory: ViewFactoryType, ViewPresentation: ViewPresentationType | |
where ModelTransformation.SrcModel == ViewPresentation.SrcView.ViewModel.Model, | |
ModelTransformation.DstModel == ViewPresentation.DstView.ViewModel.Model, | |
DstViewFactory.View == ViewPresentation.DstView>: ViewTransitionType | |
{ | |
private let viewPresentation: ViewPresentation | |
private let dstViewFactory: DstViewFactory | |
private let modelTransformation: ModelTransformation | |
init(viewPresentation: ViewPresentation, dstViewFactory: DstViewFactory, modelTransformation: ModelTransformation) { | |
self.viewPresentation = viewPresentation | |
self.dstViewFactory = dstViewFactory | |
self.modelTransformation = modelTransformation | |
} | |
func performTransition(srcView srcView: ViewPresentation.SrcView) { | |
let dstView = srcView.viewModel.model |> modelTransformation.transform |> dstViewFactory.createView | |
viewPresentation.present(srcView: srcView, dstView: dstView) | |
} | |
} | |
/// A type-erased view transition. | |
final class AnyViewTransition<SrcView: ViewType>: ViewTransitionType { | |
private let _performTransition: SrcView -> () | |
init<T: ViewTransitionType where T.SrcView == SrcView>(transition: T) { | |
self._performTransition = { transition.performTransition(srcView: $0) } | |
} | |
func performTransition(srcView srcView: SrcView) { | |
_performTransition(srcView) | |
} | |
} |
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