Scalable specification
This is the engineering specification for the Scalable interaction.
Overview
Feeds scale starting from an initial scale to a given property.
Example use:
runtime.connect(Scalable(view: view, containerView: containerView))
MVP
Expose a Scalable type
public class Scalable: Interaction
Expose configurable values
All property values should be readonly, all stream values should be settable.
class Scalable {
/** The property to which the value stream is expected to write. */
public let property: ReactiveProperty<CGFloat>
/** A stream that emits values to be written to the property. */
public var valueStream: MotionObservable<CGFloat>
/** A stream that emits velocity when the gesture recognizer ends. */
public var velocityStream: MotionObservable<CGFloat>
/** The gesture recognizer that drives this interaction. */
public let gestureRecognizer: ScaleGestureRecognizer
Expose an initializer
Allow a gesture recognizer to be optionally provided.
class Scalable {
public init(property: ReactiveProperty<CGFloat>,
containerElement: Element,
gestureRecognizer: ScaleGestureRecognizer? = nil)
Store the property
class Scalable {
init(...) {
self.property = property
...
Create a gesture recognizer if one was not provided
class Scalable {
init(...) {
...
self.gestureRecognizer = gestureRecognizer ?? ScaleGestureRecognizer()
if self.gestureRecognizer.element == nil {
containerView.addGestureRecognizer(self.gestureRecognizer)
}
...
Create the value and velocity streams
class Scalable {
init(...) {
...
let source = gestureSource(self.gestureRecognizer)
self.valueStream = source.scaled(from: property)
self.velocityStream = source.velocity()
Expose a convenience initializer
The convenience initializer should extract the necessary property from the provided element.
class Scalable {
public init(element: Element,
containerElement: Element,
gestureRecognizer: ScaleGestureRecognizer? = nil)